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# Mailshake API and MCP server

> Yes, Mailshake has a REST API for campaigns, recipients, leads and activity, with an API key from Integrations > API, but no official MCP server (checked 22 Oct 2026). The API cannot send a reply from Lead Catcher, add a follow-up to a campaign, move leads between campaigns or assign a lead.

Cold email and sales outreach tool: you upload prospects, write a sequence of emails and follow-ups, and Mailshake sends them from your mailbox and catches replies in Lead Catcher.

## What is the Mailshake API?

Cotlet's Mailshake API exposes 15 endpoints for your own Mailshake account: list campaigns, get campaign, list recipients, list replies, list leads, add recipients, pause campaign, resume campaign, pause or unpause recipient, unsubscribe recipients, set lead status, assign lead, reply to lead, move leads to campaign and add follow-up. The list_campaigns endpoint returns your team's campaigns with title, state, sender and number of emails in the sequence. Each endpoint takes simple JSON inputs like campaign_id, per_page or next_token and works both as an operation of the mailshake_read or mailshake_write MCP tool for agents and as a REST call for scripts.

- **Category:** [Marketing & SEO](https://cotlet.dev/integrations/category/marketing-seo.md)
- **Endpoints:** 15 (5 read, 10 write)
- **Updated:** 2026-10-21

Yes, Mailshake has a REST API for campaigns, recipients, leads and activity, with an API key from Integrations > API, but no official MCP server (checked 22 Oct 2026). Cotlet is a hosted MCP server and REST API for Mailshake with 15 endpoints (5 read, 10 write): you sign in once in your own cloud browser, your AI agent does the work.

## Does Mailshake have an official API?

Yes, Mailshake has a REST API for campaigns, recipients, leads and activity, with an API key from Integrations > API, but no official MCP server (checked 22 Oct 2026). The API cannot send a reply from Lead Catcher, add a follow-up to a campaign, move leads between campaigns or assign a lead.

| Task | Mailshake official | Cotlet |
|---|---|---|
| List campaigns and read their sequence | Yes | Yes |
| Add recipients to a campaign | Yes: Monthly recipient limit depends on your plan | Yes |
| Read replies, bounces and unsubscribes | Yes | Yes |
| Pause or resume a campaign or recipient | Yes | Yes |
| Set lead status | Partly: Won, lost and ignored; the API names won "closed" | Yes |
| Reply to a lead from Lead Catcher | No | Yes |
| Add a follow-up to an existing campaign | No | Yes |
| Move leads to another campaign | No | Yes |

Sources: [Mailshake API reference](https://api-docs.mailshake.com/), [Mailshake Help: API Limits](https://docs.mailshake.com/article/260-api-limits), [Mailshake Help: How do I reply to a lead?](https://docs.mailshake.com/article/133-how-do-i-reply-to-a-lead), [Zapier: Mailshake integrations](https://zapier.com/apps/mailshake/integrations)

## For AI agents

```text
Yes, Mailshake has a REST API for campaigns, recipients, leads and activity, with an API key from Integrations > API, but no official MCP server (checked 22 Oct 2026). The API cannot send a reply from Lead Catcher, add a follow-up to a campaign, move leads between campaigns or assign a lead.
Cotlet provides a hosted MCP server and REST API for Mailshake: 15 tools (5 read, 10 write).
Access       Sign up at https://cotlet.dev/app/signup?app=mailshake, then request the app and create API keys in the Cotlet console.

MCP server   https://cotlet.dev/mcp/v1
MCP tools    mailshake_read, mailshake_write, reads and writes apart; call one with {"operation": "<operation>", "arguments": {...}}
REST base    https://cotlet.dev/api/v1/mailshake, each operation at its own route, e.g. POST /api/v1/mailshake/campaigns/{campaign_id}/recipients
Auth         Authorization: Bearer <COTLET_API_KEY>. Listing endpoints and schemas needs no key; calling an endpoint needs one. Over MCP the input schemas come with sign-in.
Operations   list_campaigns, get_campaign, list_recipients, list_replies, list_leads, add_recipients, pause_campaign, resume_campaign, pause_recipient, unsubscribe_recipients, update_lead_status, assign_lead, reply_to_lead, move_leads_to_campaign, add_follow_up
Confirm      add_recipients, resume_campaign, unsubscribe_recipients, reply_to_lead, move_leads_to_campaign, add_follow_up (by default the user approves each call; the user can switch this off per tool, e.g. for scheduled automations)
Markdown     https://cotlet.dev/integrations/mailshake-api-mcp-server.md

How access works:
1. The user signs up at https://cotlet.dev/app/signup?app=mailshake, requests Mailshake in the Cotlet console and creates an API key there.
2. The user signs in to Mailshake once in their Cotlet Cloud Browser (their own Chrome in the cloud, opened from the console) and enables Mailshake for agents. An agent cannot do this step.
3. The API key goes into the MCP client or the REST call as a bearer token.

Fits: people who want a hosted Mailshake server that someone else maintains, including non-developers. Developers who prefer to run and fix code on their own computer can use an open-source Mailshake MCP server instead.

Policy: Cotlet never stores passwords, never solves CAPTCHAs, never bypasses MFA.
Company: legal details in the Terms of service at https://cotlet.dev/terms. Contact contact@cotlet.dev.
Sign-in: the user signs in to Mailshake in their own Cloud Browser, a Chrome Cotlet runs for them in the EU; password saving is off, the profile is AES-256-GCM encrypted, and agents get Mailshake only after the user enables it. Calls are requests from that browser's IP with its cookies, each listed in the user's Background activity. Disable for agents, signing out in the browser or Reset browser cuts access. Cotlet is run by Take Group sp. z o.o. (EU VAT PL6342984273).
API key: holds no Mailshake login or cookies, only asks Cotlet to run a tool. Each key is scoped to chosen apps and tools, read only or read and write. Actions that reach other people wait for the user's approval by default, so a leaked key cannot post or message as the user. Every call is in the activity log; deleting the key ends access at once.
Terms: the user stays responsible for following Mailshake's terms; Cotlet is not affiliated with Mailshake.
```

## What can an AI agent do in Mailshake?

Cotlet is best for sales teams and agencies running Mailshake who want an AI agent to answer leads, extend sequences and keep campaigns tidy without running or fixing a server.

- **[Reply to leads from Lead Catcher](https://cotlet.dev/integrations/mailshake-api-mcp-server/reply-to-leads.md)** (runs: daily): "Read my open Mailshake leads from Agency outreach Q4, draft a reply to each that asks for pricing or a call, and send them once I approve. Mark leads that say no as lost." → `list_leads`, `list_replies`, `reply_to_lead`, `update_lead_status`
- **[Add a follow-up to a running campaign](https://cotlet.dev/integrations/mailshake-api-mcp-server/add-follow-up-to-campaign.md)**: "Look at the sequence of Agency outreach Q4. If it ends after 3 emails, add a fourth as a reply in the same thread 5 days after the last one: a short note with one question." → `get_campaign`, `add_follow_up`, `list_recipients`
- **Stop drip emails for recipients who booked a meeting** (runs: daily): "Check replies from the last day in Agency outreach Q4. For everyone who confirmed a meeting, pause them in the campaign." → `list_replies`, `pause_recipient`
- **Weekly campaign and lead report** (runs: weekly): "Every Monday, list my running Mailshake campaigns with open leads, replies in the last 7 days and bounces." → `list_campaigns`, `list_leads`, `list_replies`
- **Load a prospect list into a campaign**: "Add these 40 prospects with their company name to Webinar follow-up and tell me which ones were skipped." → `list_campaigns`, `add_recipients`, `list_recipients`
- **Move interested leads into a nurture campaign**: "Move open leads from Agency outreach Q4 who asked to talk later into Webinar follow-up." → `list_leads`, `move_leads_to_campaign`, `update_lead_status`

## Can Mailshake automations run on a schedule in n8n, Make or Zapier?

Yes. Cotlet does not replace your automation platform: it gives it a Mailshake connection it does not have, with the same API key as your agent. Write actions ask for your OK by default; switch that off in your dashboard for the tools you choose, for example to reply to leads from lead catcher, and the schedule runs on its own. Cotlet runs in the cloud, so it keeps going while your computer is off.

| Where | How to connect | How to schedule |
|---|---|---|
| Your AI agent | Add https://cotlet.dev/mcp/v1 with your API key. | A scheduled agent run, for example a Claude Code routine. |
| n8n | MCP Client node with https://cotlet.dev/mcp/v1, or an HTTP Request node with the endpoint's method and URL, such as GET https://cotlet.dev/api/v1/mailshake/leads. | Schedule Trigger node. |
| Make | HTTP module: the endpoint's method and URL with an Authorization: Bearer header, and a JSON body for POST, PUT and PATCH. | Scenario schedule. |
| Zapier | Webhooks by Zapier, Custom Request: the same method, URL, header and body. | Schedule by Zapier trigger. |
| Your own script | GET https://cotlet.dev/api/v1/mailshake/leads with your API key. | cron or GitHub Actions. |

## Tools

**For AI agents:** Every endpoint and its schema is public. The 15 endpoints on this page, with parameters and example responses, can be listed without an account. Calling one returns 401 without an API key and 403 while the key has no access to Mailshake.

### list_campaigns

Your team's campaigns with title, state, sender and number of emails in the sequence. Access: read. REST: `GET /api/v1/mailshake/campaigns`. MCP: `mailshake_read → list_campaigns`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `search` | string | no | Only campaigns whose title matches this text. |
| `per_page` | integer | no | 1 to 100. Default: 100. |
| `next_token` | string | no | Next page token from the previous call. |

Lists the campaigns of your Mailshake team, 100 to a page. is_paused and is_archived show the state; an archived campaign has to be unarchived in the Mailshake app before most other tools work on it. Pass next_token back to get the next page; it is null on the last page. Use id as campaign_id in the other tools.

Example response:

```json
{
  "results": [
    {
      "id": 4821,
      "title": "Agency outreach Q4",
      "is_paused": false,
      "is_archived": false,
      "sender": "sam@northwind.example",
      "emails_in_sequence": 3,
      "created": "2026-10-02T09:14:00.000Z"
    },
    {
      "id": 4790,
      "title": "Webinar follow-up",
      "is_paused": true,
      "is_archived": false,
      "sender": "sam@northwind.example",
      "emails_in_sequence": 2,
      "created": "2026-09-18T12:40:00.000Z"
    }
  ],
  "next_token": null
}
```

### get_campaign

One campaign with its message sequence: initial email, follow-ups, drips and on-click emails. Access: read. REST: `GET /api/v1/mailshake/campaigns/{campaign_id}`. MCP: `mailshake_read → get_campaign`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | yes | Campaign ID from list_campaigns. |

Returns one campaign and every message of its sequence in sending order. type is initial, follow-up, drip or on-click. reply_to_id is set on a follow-up and points to the first message of its reply chain, so follow-ups sent as replies share one thread. A campaign the team cannot see comes back as not_found. Read this before add_follow_up to see how long the sequence is.

Example response:

```json
{
  "id": 4821,
  "title": "Agency outreach Q4",
  "is_paused": false,
  "is_archived": false,
  "sender": {
    "email_address": "sam@northwind.example",
    "from_name": "Sam Rivera"
  },
  "messages": [
    {
      "id": 90311,
      "type": "initial",
      "subject": "Quick question about your client reporting",
      "reply_to_id": null,
      "is_paused": false
    },
    {
      "id": 90312,
      "type": "follow-up",
      "subject": null,
      "reply_to_id": 90311,
      "is_paused": false
    },
    {
      "id": 90313,
      "type": "follow-up",
      "subject": null,
      "reply_to_id": 90311,
      "is_paused": false
    }
  ],
  "url": "https://mailshake.com/app/#/2210/campaigns/4821/overview"
}
```

### list_recipients

Recipients of a campaign, searchable and filterable by what they did. Access: read. REST: `GET /api/v1/mailshake/campaigns/{campaign_id}/recipients`. MCP: `mailshake_read → list_recipients`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | yes | Campaign ID from list_campaigns. |
| `filter_action` | enum | no | opened, clicked, replied, was_sent, bounced, paused or has_problems. |
| `negate` | boolean | no | true to find recipients who did NOT take the filter_action. Default: false. |
| `search` | string | no | Only recipients matching this name or email address. |
| `per_page` | integer | no | 1 to 100. Default: 100. |
| `next_token` | string | no | Next page token from the previous call. |

Lists the recipients of one campaign, 100 to a page, with their custom fields and whether they are paused. filter_action keeps only recipients who opened, clicked, replied, were sent a message, bounced, are paused or have problems (a missing text replacement or a failed send). negate flips the filter, so opened with negate returns recipients who never opened. Pass next_token back for the next page.

Example response:

```json
{
  "results": [
    {
      "id": 771204,
      "email_address": "dana@brightpath.example",
      "full_name": "Dana Whitfield",
      "is_paused": false,
      "fields": {
        "company": "Brightpath"
      }
    },
    {
      "id": 771205,
      "email_address": "omar@lumenlabs.example",
      "full_name": "Omar Haddad",
      "is_paused": false,
      "fields": {
        "company": "Lumen Labs"
      }
    }
  ],
  "next_token": null
}
```

### list_replies

Most recent replies, bounces, out-of-office notes and unsubscribes with the message text. Access: read. REST: `GET /api/v1/mailshake/replies`. MCP: `mailshake_read → list_replies`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `reply_type` | enum | no | reply, bounce, out-of-office, unsubscribe or delay-notification. Default: all types. |
| `campaign_id` | integer | no | Only replies in this campaign. |
| `recipient_email_address` | string | no | An address, or part of one such as a domain. |
| `per_page` | integer | no | 1 to 25. Default: 25. |
| `next_token` | string | no | Next page token from the previous call. |

Returns the newest replies to your sent emails, 25 to a page, newest first. type tells a real reply from a bounce, an out-of-office note, an unsubscribe or a delay notification; pass reply_type reply to get only real replies. Each item carries the plain-text body, the campaign and the recipient. recipient_email_address also matches part of an address, so a domain finds everyone at that company.

Example response:

```json
{
  "results": [
    {
      "reply_id": 88140,
      "type": "reply",
      "action_date": "2026-10-21T14:12:00.000Z",
      "recipient": {
        "id": 771204,
        "email_address": "dana@brightpath.example",
        "full_name": "Dana Whitfield"
      },
      "campaign": {
        "id": 4821,
        "title": "Agency outreach Q4"
      },
      "subject": "Re: Quick question about your client reporting",
      "body": "Hi Sam, we are open to a call. What does pricing look like?"
    }
  ],
  "next_token": null
}
```

### list_leads

Leads from Lead Catcher with status, campaign, recipient and who they are assigned to. Access: read. REST: `GET /api/v1/mailshake/leads`. MCP: `mailshake_read → list_leads`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | no | Only leads from this campaign. |
| `status` | enum | no | open, won, lost or ignored. Default: all. |
| `assigned_to_email` | string | no | Only leads assigned to this teammate. |
| `search` | string | no | Only leads matching this name or email address. |
| `per_page` | integer | no | 1 to 100. Default: 100. |
| `next_token` | string | no | Next page token from the previous call. |

Lists leads, 100 to a page. A lead is a recipient who replied, or who matched the capture rules of the campaign. status is open, won, lost or ignored. Open leads need handling. assigned_to is the teammate who owns the lead, by default the person the campaign is assigned to. Use lead_id in update_lead_status, assign_lead, reply_to_lead and move_leads_to_campaign.

Example response:

```json
{
  "results": [
    {
      "lead_id": 5530,
      "status": "open",
      "created": "2026-10-21T14:12:00.000Z",
      "campaign": {
        "id": 4821,
        "title": "Agency outreach Q4"
      },
      "recipient": {
        "id": 771204,
        "email_address": "dana@brightpath.example",
        "full_name": "Dana Whitfield"
      },
      "assigned_to": "lucy@northwind.example"
    },
    {
      "lead_id": 5531,
      "status": "open",
      "created": "2026-10-21T16:40:00.000Z",
      "campaign": {
        "id": 4821,
        "title": "Agency outreach Q4"
      },
      "recipient": {
        "id": 771205,
        "email_address": "omar@lumenlabs.example",
        "full_name": "Omar Haddad"
      },
      "assigned_to": "lucy@northwind.example"
    }
  ],
  "next_token": null
}
```

### add_recipients

Add people to a campaign with a name and custom fields for the text replacements in your emails. Access: write, asks the user first. REST: `POST /api/v1/mailshake/campaigns/{campaign_id}/recipients`. MCP: `mailshake_write → add_recipients`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | yes | Campaign ID from list_campaigns. |
| `addresses` | object[] | yes | Each item: email_address (required), full_name, and fields, an object of custom values such as company. Mailshake adds first, last and name text replacements from full_name. Up to 30 fields per recipient. |
| `add_as_new_list` | boolean | no | true to keep these recipients grouped as their own list. Default: false, they join the last list you uploaded. |

Adds recipients to a campaign and waits for Mailshake to finish the import, then returns what was skipped. Addresses on your unsubscribe list and addresses already in the campaign are skipped. A campaign holds up to 5,000 recipients through the API, and your plan limits how many recipients you can add per month. Unless the campaign is paused, new recipients are scheduled to get its emails right away. A field your emails use as a text replacement but a recipient lacks keeps that recipient's emails from being scheduled. By default you confirm each call; you can switch that off for this tool.

Example response:

```json
{
  "campaign_id": 4821,
  "submitted": 3,
  "added": 2,
  "invalid_emails": [],
  "problems": {
    "unsubscribed_emails": [
      "li@oldclient.example"
    ],
    "already_in_campaign_emails": [],
    "over_campaign_limit_emails": []
  }
}
```

### pause_campaign

Stop all sending for a campaign right away. Access: write. REST: `POST /api/v1/mailshake/campaigns/{campaign_id}/pause`. MCP: `mailshake_write → pause_campaign`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | yes | Campaign ID from list_campaigns. |

Pauses a campaign. A batch of emails already being sent is not stopped. It reaches no one and resume_campaign undoes it, so it does not wait for your OK. Recipients keep their place in the sequence.

Example response:

```json
{
  "campaign_id": 4821,
  "is_paused": true
}
```

### resume_campaign

Start sending again for a paused campaign. Access: write, asks the user first. REST: `POST /api/v1/mailshake/campaigns/{campaign_id}/resume`. MCP: `mailshake_write → resume_campaign`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | yes | Campaign ID from list_campaigns. |

Resumes a paused campaign. The sending calendar of your team reschedules itself around the pending emails of this campaign, which can take up to 5 minutes to show in the calendar. Emails then go out to every recipient who is due one. By default you confirm each call; you can switch that off for this tool.

Example response:

```json
{
  "campaign_id": 4790,
  "is_paused": false
}
```

### pause_recipient

Stop or restart the emails of one recipient in one campaign and keep the rest of the campaign running. Access: write. REST: `POST /api/v1/mailshake/campaigns/{campaign_id}/recipient/pause`. MCP: `mailshake_write → pause_recipient`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | yes | The campaign the recipient is in. |
| `email_address` | string | yes | The recipient's email address. |
| `paused` | boolean | no | true to pause, false to unpause. Default: true. |

Pauses one recipient in one campaign by email address, or unpauses them with paused false. An email being sent at that moment is not stopped. A reply stops follow-ups but not drip emails, so this is how you stop a drip for someone who booked a meeting. Unpausing reschedules their pending emails. It reaches no one and one more call reverses it, so it does not wait for your OK. A recipient not in the campaign comes back as not_found.

Example response:

```json
{
  "campaign_id": 4821,
  "email_address": "omar@lumenlabs.example",
  "is_paused": true
}
```

### unsubscribe_recipients

Add email addresses to your team's unsubscribe list so no campaign emails them again. Access: write, asks the user first. REST: `POST /api/v1/mailshake/recipients/unsubscribe`. MCP: `mailshake_write → unsubscribe_recipients`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `email_addresses` | string[] | yes | Addresses to unsubscribe. |

Adds a list of addresses to the unsubscribe list of your team. It applies to every campaign, and add_recipients skips these addresses from then on. This tool cannot remove an address from the list again. By default you confirm each call; you can switch that off for this tool.

Example response:

```json
{
  "unsubscribed": [
    "li@oldclient.example"
  ]
}
```

### update_lead_status

Mark a lead won, lost or ignored, or open it again. Access: write. REST: `PATCH /api/v1/mailshake/leads/{lead_id}/status`. MCP: `mailshake_write → update_lead_status`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `lead_id` | integer | yes | Lead ID from list_leads. |
| `status` | enum | yes | won, lost, ignored or open. |

Sets the status of one lead. Won and lost close a lead you handled; ignored marks a lead not worth pursuing; open puts it back in the queue. Mailshake syncs these status events to HubSpot, Pipedrive or Salesforce if your team connected one. It reaches no one and one more call reverses it, so it does not wait for your OK.

Example response:

```json
{
  "lead_id": 5531,
  "status": "ignored"
}
```

### assign_lead

Give an open lead to a teammate, or set it to unassigned so anyone can take it. Access: write. REST: `POST /api/v1/mailshake/leads/{lead_id}/assign`. MCP: `mailshake_write → assign_lead`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `lead_id` | integer | yes | Lead ID from list_leads. |
| `assignee_email` | string | no | Email of a teammate. Leave out to set the lead to unassigned. |

Changes who owns a lead in Lead Catcher. New leads go to the teammate the campaign is assigned to; this changes one lead. The assignee must be a user of your Mailshake team. It reaches no one outside your team and one more call reverses it, so it does not wait for your OK.

Example response:

```json
{
  "lead_id": 5530,
  "assigned_to": "lucy@northwind.example"
}
```

### reply_to_lead

Send an email reply to a lead from Lead Catcher, as you would with the Reply button. Access: write, asks the user first. REST: `POST /api/v1/mailshake/leads/{lead_id}/replies`. MCP: `mailshake_write → reply_to_lead`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `lead_id` | integer | yes | Lead ID from list_leads. |
| `body` | string | yes | Plain-text body of the reply. |
| `move_to_campaign_id` | integer | no | Also add the lead to this campaign when the reply is sent. |

Sends one email to the lead from your Mailshake mailbox. Mailshake records it as a one-off send, not a campaign email. If the lead answers, the lead opens again in your queue. Pass move_to_campaign_id to add the person to another campaign in the same step; the campaign must exist and not be a draft. The body is plain text. A sent email cannot be recalled. By default you confirm each call; you can switch that off for this tool.

Example response:

```json
{
  "lead_id": 5530,
  "status": "sent",
  "sent_as": "one-off",
  "to": "dana@brightpath.example",
  "subject": "Re: Quick question about your client reporting",
  "sent_at": "2026-10-22T08:05:00.000Z"
}
```

### move_leads_to_campaign

Add leads to another campaign, as the Add to Campaign action in Lead Catcher does. Access: write, asks the user first. REST: `POST /api/v1/mailshake/campaigns/{campaign_id}/leads-to-campaign/move`. MCP: `mailshake_write → move_leads_to_campaign`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `lead_ids` | integer[] | yes | Lead IDs from list_leads. |
| `campaign_id` | integer | yes | The campaign to add them to. |

Adds the people behind the leads to a running campaign, so they start its sequence. The target campaign must exist and not be a draft, and its prospect limit still applies (5,000 on the Email Outreach plan, 10,000 on Sales Engagement). Adding a person here does not pause them in the campaign they came from. Leads that did not fit come back in skipped. By default you confirm each call; you can switch that off for this tool.

Example response:

```json
{
  "campaign_id": 4790,
  "moved": 2,
  "skipped": []
}
```

### add_follow_up

Add a follow-up email at the end of a campaign's sequence, with a delay after the previous email. Access: write, asks the user first. REST: `POST /api/v1/mailshake/campaigns/{campaign_id}/follow-ups`. MCP: `mailshake_write → add_follow_up`.

| Parameter | Type | Required | Description |
|---|---|---|---|
| `campaign_id` | integer | yes | Campaign ID from list_campaigns. |
| `body` | string | yes | Body of the follow-up. Text replacements such as {{first}} work. |
| `delay_days` | integer | yes | Days to wait after the previous email in the sequence. |
| `reply_to_previous` | boolean | no | true to send as a reply in the same thread. Default: true. |
| `subject` | string | no | Subject line. Needed only when reply_to_previous is false. |

Appends a follow-up to the sequence of a campaign. With reply_to_previous true it goes out as a reply in the same thread and has no subject of its own; with false it is a new email and needs subject. Follow-ups stop for a recipient who replies or becomes a lead, and bounced or unsubscribed recipients get none. On a campaign that already ran, the delay counts from each recipient's last send, so recipients who waited longer get the email at once. By default you confirm each call; you can switch that off for this tool.

Example response:

```json
{
  "campaign_id": 4821,
  "message_id": 90314,
  "type": "follow-up",
  "position": 4,
  "reply_to_id": 90311,
  "delay_days": 5,
  "subject": null
}
```

## How do I connect Mailshake to Claude Code, Codex or Cursor?

Connecting Mailshake takes three steps: sign up, sign in to Mailshake once in your Cloud Browser and enable it for agents, then add one MCP server or call the REST API with the same key.

### Connect Mailshake to your agent.

1. **Create an account** Sign up and add Mailshake in the console. Your API key is there too.

2. **Sign in to Mailshake in your Cloud Browser** Open your Cloud Browser in the console: your own Chrome in the cloud. Sign in to Mailshake there yourself, the way you always do, then press Enable for agents, read only or read and write. We never save your password, and your agent keeps working even when your computer is off.

3. **Add Cotlet to your agent** Paste the snippet for your client. The same server and key serve every app you connect, so you do this once.

   Claude Code:

```
claude mcp add --transport http cotlet \
  https://cotlet.dev/mcp/v1 \
  --header "Authorization: Bearer $COTLET_API_KEY"
```

   Cursor:

```
{
  "mcpServers": {
    "cotlet": {
      "url": "https://cotlet.dev/mcp/v1",
      "headers": {
        "Authorization": "Bearer ${COTLET_API_KEY}"
      }
    }
  }
}
```

   Codex:

```
# ~/.codex/config.toml
[mcp_servers.cotlet]
url = "https://cotlet.dev/mcp/v1"
bearer_token_env_var = "COTLET_API_KEY"
```

4. **Ask your agent** Ask in plain words. Your agent finds the Mailshake tools on the server and calls them for you; anything that reaches other people waits for your OK unless you switch that off for a tool.

```
Read my open Mailshake leads from Agency outreach Q4, draft a reply to each that asks for pricing or a call, and send them once I approve. Mark leads that say no as lost.
```

### Call Mailshake from your scripts.

1. **Export your API key** Your scripts use the same API key as your agent. Keep it in an environment variable, never in your code.

```
export COTLET_API_KEY="cotlet_..."
```

2. **Call a tool** Every tool is an endpoint under /api/v1/mailshake with its own method and path, listed with the endpoints above. Path parameters go in the URL; the other parameters go in the query for GET and DELETE and in a JSON body otherwise.

```
curl -X POST https://cotlet.dev/api/v1/mailshake/campaigns/4821/recipients \
  -H "Authorization: Bearer $COTLET_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"addresses":[{"email_address":"dana@brightpath.example","full_name":"Dana Whitfield","fields":{"company":"Brightpath"}},{"email_address":"omar@lumenlabs.example","full_name":"Omar Haddad","fields":{"company":"Lumen Labs"}},{"email_address":"li@oldclient.example","full_name":"Li Chen","fields":{"company":"Old Client"}}],"add_as_new_list":true}'
```

3. **Read the result** You get plain JSON back, ready for your script. A failed call costs nothing.

```
{
  "campaign_id": 4821,
  "submitted": 3,
  "added": 2,
  "invalid_emails": [],
  "problems": {
    "unsubscribed_emails": [
      "li@oldclient.example"
    ],
    "already_in_campaign_emails": [],
    "over_campaign_limit_emails": []
  }
}
```

## Why use Cotlet for Mailshake?

**Built for agents**

- One MCP server for every app you connect.
- The same tools as a REST API for scripts and cron jobs.
- Works with Claude Code, Codex and Cursor.

**Your login stays yours**

- You sign in to Mailshake yourself, in your own Cloud Browser. We never save your password; the profile is encrypted with AES-256-GCM, the cipher 1Password uses.
- A+ on Qualys SSL Labs, securityheaders.com and Mozilla Observatory.
- The model never sees a login.
- No stored passwords, no CAPTCHA solving, no MFA bypass.

**You stay in control**

- Scope each API key: its apps, its tools, read only or read and write.
- Anything that reaches other people waits for your OK, so a leaked key cannot post or message as you.
- Every background request listed in your Background activity. Disable for agents in one click.

**Kept working for you**

- We test every integration every 6 hours.
- When Mailshake changes, the tool pauses until we fix it.
- Failed calls cost nothing.

## Is it safe to connect Mailshake to Cotlet?

Yes. You sign in to Mailshake yourself, in your own Cloud Browser, and we never save your password. Your agents only get Mailshake once you enable it, and every background request is listed. The browser profile is stored encrypted with AES-256-GCM, the same cipher 1Password uses for its vaults and Apple for iCloud Keychain. Independent public scanners grade cotlet.dev A+ and find it clean; click a result to rerun it yourself.

- **A+ on Qualys SSL Labs**: Encryption in transit: TLS setup and certificates, on all four server addresses. [Live result](https://www.ssllabs.com/ssltest/analyze.html?d=cotlet.dev)
- **A+ on securityheaders.com**: Browser protections sent with every page, all six headers present. [Live result](https://securityheaders.com/?q=cotlet.dev&followRedirects=on)
- **A+ on Mozilla Observatory**: Mozilla's web security baseline: score 120 of 100, 12 of 12 tests passed. [Live result](https://developer.mozilla.org/en-US/observatory/analyze?host=cotlet.dev)
- **Clean on Sucuri SiteCheck**: No malware, spam or defacement, and not on any of 9 blocklists, Google Safe Browsing included. [Live result](https://sitecheck.sucuri.net/results/cotlet.dev)

[How Cotlet protects your access](https://cotlet.dev/security.md)

### Common concerns

**Who runs Cotlet?**

Cotlet is run by Take Group, a Polish software company working since 2019. Take Group runs about 3,200 websites on its own systems and has its own DevOps team for infrastructure security. We built and used integrations like this inside the company for years before opening them as Cotlet.

**Is this an official Mailshake integration?**

No, Cotlet is independent of Mailshake. Mailshake's own API is too limited for this work. Cotlet works through your own Mailshake account, the way you use Mailshake in the browser, so you need no partner approval and no developer setup.

**What about client data and GDPR?**

Cotlet is run from the EU and follows the GDPR. Cloud Browsers run in Finland, a Tier 1 country in the ITU Global Cybersecurity Index 2024. Data passes through a call and is not kept after it.

**Can I start with read only?**

Yes. Enable the app for agents as read only, or make the API key read only, and anything that reaches other people waits for your OK unless you switch that off per tool.

**Is it reliable?**

Every Cotlet service is checked every 3 minutes from Europe, North America, Asia and Australia. The live results and any outage are public at status.cotlet.dev.

**How do I stop?**

Press Disable for agents next to Mailshake in your console: your agents lose access at once and you stay signed in. Signing out of Mailshake in the browser works too, and Reset browser deletes the whole profile.

## Is there a Mailshake MCP server on GitHub?

Yes. Community Mailshake MCP servers exist, usually maintained by one person. They wrap the REST API with your API key, so they cover campaigns, recipients and leads but not replies from Lead Catcher or follow-ups. You install and fix them yourself. Cotlet hosts the same kind of server for you, adds the Lead Catcher and campaign actions the API lacks, and our team keeps it working.

|  | GitHub MCP server | Cotlet |
|---|---|---|
| Setup | Clone the repo, create an API key, add it to each MCP client | Sign up, sign in to Mailshake once, add one MCP server or API key |
| When Mailshake changes | It breaks until you or the maintainer fix it | Our team tests it daily and fixes it for you; failed calls are free |
| Your Mailshake access | An API key in a file on your computer, readable by any program you run | Your own Cloud Browser in the EU, session encrypted, only for the apps you enable, disabled for agents in one click |
| When access ends | Tools fail until you create a new key by hand | If Mailshake logs you out, your agent gets a link to sign in again |
| Upkeep | You update, monitor and debug it yourself | Nothing to host or update |
| Where it runs | Your computer, while it is on | Hosted: Claude Code, Codex, Cursor, n8n and scripts, also on a schedule |
| Price | Free, paid for with your time | Free 7-day trial, then pay-as-you-go credit packs, no subscription |

### Which one fits you

**Pick Cotlet if**

- you are not a developer, or you do not want to maintain a server
- you need it to keep working when Mailshake changes, without checking it yourself
- your agent or a script should run it on a schedule, also while your computer is off

**Pick an open-source server if**

- you are comfortable installing, updating and fixing it yourself
- you want your sign-in to stay on your own computer
- you only need it now and then, from one MCP client

## How much does the Mailshake API cost?

Free 7-day trial with 2,000 credits, no card needed. After that, the Mailshake API is pay as you go with no limit on apps: Credit packs from $29 for 5,000 credits, one-time, no subscription. A successful call uses 20 to 30 credits (25 for most tools, about $0.10 to $0.15), your Cloud Browser uses 50 credits a day while it has an app enabled for agents, however many apps that is, and an agent driving the browser itself uses 5 credits a minute. Credit packs stay valid for 12 months and stack, so unused credits carry over.

| Credits | Price, one time | Calls at 25 credits | Per 1,000 credits |
|---|---|---|---|
| 5,000 | $29 | 200 | $5.80 |
| 15,000 | $79 | 600 | $5.27 |
| 32,000 | $149 | 1,280 | $4.66 |
| 60,000 | $249 | 2,400 | $4.15 |

Only successful calls use credits; failed calls and timeouts cost nothing. At a balance of 0 calls pause, never a surprise charge. Authenticate with the `Authorization: Bearer` header. [See full pricing](https://cotlet.dev/pricing.md)

## How Cotlet holds your access

Cotlet hosts MCP servers and REST APIs for apps with no usable API. Your agent works in your own Mailshake account.

- **Company details:** Cotlet is run by Take Group sp. z o.o., a company registered in Poland. Its full address and registration numbers are in the Terms of service. [Terms of service](https://cotlet.dev/terms)
- **Your sign-in:** You sign in to Mailshake yourself, in your own Cloud Browser: a Chrome we run for you in the EU, one per app. We never save your password (password saving is off), the profile is stored encrypted with AES-256-GCM, and your agents get Mailshake only after you enable it. When Mailshake signs you out, your agent gives you a link to sign in again. [Security](https://cotlet.dev/security.md)
- **Revoking access:** Press Disable for agents next to Mailshake, sign out of Mailshake in your Cloud Browser, or reset the browser. Every background request is listed in your Background activity. Actions that reach other people wait for your OK unless you switch that off per tool.
- **What we never do:** Store passwords, solve CAPTCHAs or bypass MFA.
- **Mailshake's terms:** You use your own Mailshake account and stay responsible for following Mailshake's terms. Cotlet is independent and not affiliated with Mailshake. [Terms](https://cotlet.dev/terms)
- **Contact:** Questions about the company, security or an app: [contact@cotlet.dev](mailto:contact@cotlet.dev)

## Frequently asked questions

**How do I get access?**

Sign up free, open Mailshake in the console and press Request access. Then you create your API key and connect Mailshake there.

**Do I need to be technical?**

No. You sign in to Mailshake once in your Cloud Browser, a normal Chrome you open from the console, and paste one command into your agent, or one URL into n8n. Your agent can walk you through it. There is no server to install, update or fix.

**Is it safe to connect Mailshake to Cotlet?**

Yes. You sign in to Mailshake yourself, in your own Cloud Browser in the EU, and we never save your password. Your agents only get Mailshake once you enable it, every background request is listed, and the browser profile is stored encrypted with AES-256-GCM, the cipher 1Password uses for its vaults. The AI model never sees a login, posts and messages wait for your OK, and Disable for agents cuts access in one click. Independent scanners grade cotlet.dev A+ on Qualys SSL Labs, securityheaders.com and Mozilla Observatory; live results are on https://cotlet.dev/security.

**Is a hosted server safer than a local one? My Mailshake sign-in would leave my computer.**

On Cotlet you sign in inside your own Cloud Browser, which only you open, and its profile is stored encrypted with AES-256-GCM in the EU. Agents get only the apps you enable, and every background request is listed. A local server keeps your Mailshake cookie in a plain file on your computer, readable by any program you run, and stops when your computer is off.

**Why does Cotlet send requests instead of clicking in my browser?**

To be fast, Cotlet doesn't click through Mailshake's pages. It sends the same requests your browser would, from your browser's IP with its cookies, without opening a window. Mailshake sees the same browser and IP you signed in with, and every request is listed in your Background activity.

**What if someone gets my Cotlet API key?**

The key holds no Mailshake login or cookies, it only asks Cotlet to run a tool. It can call only the apps and tools you gave it, and a read-only key changes nothing. Anything that reaches other people, like posts, comments or messages, waits for your OK in the dashboard by default, so a leaked key cannot post or message as you. When you switch approval off for a scheduled job, give that job its own key limited to that one tool. Every call is in your activity log, and deleting the key ends access at once.

**Why a signed-in browser and not OAuth, like other integration platforms?**

Mailshake offers no OAuth token you can simply grant for these tools: its official API leaves them out or needs a developer app, a plan or an approval first (see the official API section above). That is why Cotlet sets the limits itself: per key, per tool, with your approval before anything reaches other people. Cotlet is run by Take Group sp. z o.o., an EU company (VAT PL6342984273).

**Do I need a Mailshake API key or a certain plan?**

No key. Cotlet works in your signed-in Mailshake account and does not use the API. Mailshake does not tie its API to one plan in its help center: limits for API calls per hour and for recipients added per month depend on your plan and grow with each user seat.

**How many recipients can a campaign hold?**

Mailshake's API reference says up to 5,000 recipients per campaign. Its help center gives 5,000 prospects on the Email Outreach plan and 10,000 on Sales Engagement. add_recipients lists the addresses that did not fit in over_campaign_limit_emails.

**Can my agent post or send messages in Mailshake without asking me?**

No. Every call to add_recipients, resume_campaign, unsubscribe_recipients, reply_to_lead, move_leads_to_campaign or add_follow_up waits for your OK by default. For scheduled automations you can switch confirmation off per tool in your dashboard, for example only for approvals. pause_campaign, pause_recipient, update_lead_status, assign_lead runs without asking, because it sends nothing to anyone and one call undoes it.

**Can I use the Mailshake API in n8n?**

Yes. Add https://cotlet.dev/mcp/v1 with your API key in n8n's MCP Client node, or call its endpoints under https://cotlet.dev/api/v1/mailshake from the HTTP Request node.

---

Give your AI agents your signed-in browser.

**Product:** [Integrations](https://cotlet.dev/integrations.md) · [Use cases](https://cotlet.dev/use-cases.md) · [How it works](https://cotlet.dev/how-it-works.md) · [Pricing](https://cotlet.dev/pricing.md) · [Security](https://cotlet.dev/security.md)

**Resources:** [Blog](https://cotlet.dev/blog.md) · [API docs](https://cotlet.dev/docs.md) · [Help center](https://cotlet.dev/help.md) · [Changelog](https://cotlet.dev/changelog.md) · [GitHub](https://github.com/cotletdev/cotlet)

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**Elsewhere:** [Status page](https://status.cotlet.dev) · [Cotlet on GitHub](https://github.com/cotletdev) · [Cotlet on X](https://x.com/cotletdev) · [Cotlet on LinkedIn](https://www.linkedin.com/company/cotletdev) · [Cotlet on Product Hunt](https://www.producthunt.com/products/cotlet) · [Cotlet on Crunchbase](https://www.crunchbase.com/organization/cotlet) · [Cotlet on SaaSHub](https://www.saashub.com/cotlet)

Cotlet is an independent service. It is not affiliated with, endorsed by or sponsored by any of the products listed on this site. Product names are trademarks of their respective owners.

## For AI agents: sign your user up

Is your user asking you to sign them up for Cotlet? You can do it for them, no account or key needed.

1. Read the fields and their allowed values: GET https://cotlet.dev/api/v1/access-requests
2. Ask the user for each value: email, apps, what you will do with them. If they leave the password to you, generate a strong one and show it to them.
3. Show the user what you will send, then POST it as JSON to https://cotlet.dev/api/v1/access-requests.

One call creates the account and sends the access request; we email the user when access is granted.