Developer Tools

Mailosaur MCP Server

Use Studio chat to drive this server — credentials stay in your workspace.

Mailosaur is an email and SMS testing platform that lets developers capture, inspect, search, and analyze messages sent by applications. Use it to automate email verification flows, test deliverability (SPF/DKIM/DMARC/SpamAssassin), and manage virtual inboxes (servers) for isolated test environments.

17 tools
Agent guide included
API Key
Start Chatting

Opens MCPBundles Studio with this server selected. After sign-in, chat and run tools from the same thread.

Browse all tools

AI Skill
SKILL.md

Domain knowledge for Mailosaur — workflow patterns, data models, and gotchas for your AI agent.

Mailosaur

Mailosaur is an email and SMS testing platform for capturing, inspecting, and analyzing messages during development and CI/CD.

Data Model

  • Servers — virtual inboxes identified by an 8-char ID (e.g. knyrbtfl). Each server has a unique catch-all address *@SERVER_ID.mailosaur.net. Any email sent to that domain is captured.
  • Messages — emails or SMS captured by a server. Summary includes id, from, to, subject, received date. Full detail adds HTML/text body, links, images, attachments, and SMTP headers.
  • Attachments — files on messages, downloadable via the Files API.
  • Deliverability Reports — per-message analysis: SPF, DKIM, DMARC, blocklists, content flags, SpamAssassin score.
  • Usage — account limits (servers, users, emails, SMS) and 31-day transaction history.

Common Workflows

  1. Verify signup email: Create or reuse a server → trigger signup with user@SERVER_ID.mailosaur.net → search messages by sentTo → extract verification link from html.links.
  2. Test deliverability: Open the captured message id → run deliverability report → check SPF/DKIM/DMARC pass and SpamAssassin score.
  3. CI cleanup: Delete all messages on a server between test runs to avoid stale matches.

Gotchas

  • server is required for listing and searching messages. Discover the server id from the server directory before message operations.
  • Search bodies: Message search expects a JSON body with criteria—not a bare keyword on the URL line.
  • Messages arrive asynchronously — if searching immediately after sending, results may be empty. Client libraries usually retry; automation should briefly poll before declaring a miss.
  • Deliverability reports require the message to have been received (not just created/sent via the API).

Tools in this Server (17)

Mailosaur Create Server

Create a new Mailosaur server (virtual inbox). Returns the new server with its ID. Send test emails to any-address@SERVER_ID.mailosaur.net to capture ...

Mailosaur Delete All Msgs

Permanently delete ALL messages and attachments in a server. Useful for cleaning up between test runs. This cannot be undone.

Mailosaur Delete Message

Permanently delete a single message and its attachments. This cannot be undone.

Mailosaur Delete Server

Permanently delete a Mailosaur server and all its messages and attachments. This cannot be undone.

Mailosaur Forward Message

Forward an email message to a verified external email address. You must provide at least one of 'html' or 'text' as the forwarding body. Optionally ov...

Mailosaur Generate Otp

Generate a one-time password (OTP/TOTP) from a base32-encoded shared secret. Use this to automate 2FA verification flows in tests. Returns the current...

Mailosaur Get Deliverability

Run a deliverability analysis on a received message. Returns SPF, DKIM, DMARC results, blocklist checks, content flags, DNS records, and a SpamAssassi...

Mailosaur Get Email Source

Download the raw EML source of an email message. Returns the full RFC 5322 email source including all MIME headers, which is useful for debugging deli...

Mailosaur Get Messages

Get Mailosaur messages. Pass message_id for full message details (HTML body, text body, links, images, attachments, SMTP headers). Omit message_id to ...

Mailosaur Get Server Pwd

Retrieve the SMTP/POP3 password for a server. Use this password with the server ID as username to configure applications that send email via SMTP (hos...

Mailosaur Get Servers

Get Mailosaur servers (virtual inboxes). Pass server_id to retrieve a single server, or omit to list all servers with their IDs, names, and message co...

Mailosaur Get Usage Limits

Retrieve current Mailosaur account usage limits and consumption. Shows limits and current usage for servers, users, email, SMS, previews, and phone nu...

Mailosaur Get Usage Txns

Retrieve the last 31 days of usage transactions. Shows daily counts of emails received, emails sent, SMS, previews, and screenshots.

Mailosaur Reply To Message

Reply to an email message. The original message must have been received from an external sender (not created via send_email with send=false). You must...

Mailosaur Search Messages

Search for messages matching criteria within a Mailosaur server. Filter by sender, recipient, subject, or body text. Returns message summaries — use g...

Mailosaur Send Email

Send an email from a Mailosaur server. The recipient must be a verified external email address in your Mailosaur account. Set 'send' to false to creat...

Mailosaur Update Server

Update a Mailosaur server (rename an inbox). Returns the updated server.

Frequently Asked Questions

What is the Mailosaur MCP server?

Mailosaur is an email and SMS testing platform that lets developers capture, inspect, search, and analyze messages sent by applications. Use it to automate email verification flows, test deliverability (SPF/DKIM/DMARC/SpamAssassin), and manage virtual inboxes (servers) for isolated test environments. It provides 17 tools that AI agents can use through the Model Context Protocol (MCP).

How do I connect Mailosaur to my AI agent?

Add the MCPBundles server URL to your MCP client configuration (Claude Desktop, Cursor, VS Code, etc.). The URL format is: https://mcp.mcpbundles.com/bundle/mailosaur. Authentication is handled automatically.

How many tools does Mailosaur provide?

Mailosaur provides 17 tools that can be called by AI agents, along with a SKILL.md that gives your AI agent domain knowledge about when and how to use them.

What authentication does Mailosaur require?

Mailosaur uses API Key. Mailosaur requires credentials. Connect via MCPBundles and authentication is handled automatically.

Setup Instructions

Connect Mailosaur to any MCP client in minutes

https://mcp.mcpbundles.com/bundle/mailosaur

What is MCP?

Model Context Protocol lets AI tools call external capabilities securely through a single URL. This bundle groups tools behind an MCP endpoint that many clients can use.

Use this bundle in 3 steps

  1. Copy the MCP URL above
  2. Open your AI tool and add a new MCP/connector
  3. Paste the URL and follow any auth prompts

Claude Desktop Users

Skip the manual setup! Use the .mcpb file format for one-click installation. Check the Claude Desktop tab for setup instructions.

Pick your tool tab for exact steps

Select ChatGPT, Cursor, Claude Code, or another tab for copy-paste config.

Ready to chat with Mailosaur?

Same flow: Studio opens on this server after sign-in. Keep chatting to call tools from the conversation.

Mailosaur MCP Server & Skill — 17 Tools