Introduction

Mailcycle is private email infrastructure with an HTTP API. Everything the Mailcycle apps do goes through this API, so your code can create email addresses, pair devices, read mail and send it.

The API lives at:

https://api.mailcycle.email

It speaks JSON and authenticates with a bearer token: an API key on Operator and above, or a session from the recovery-phrase handshake on any plan.

What comes back encrypted

Message content and attachments are sealed to the address’s key as soon as they arrive. Address labels and device names are sealed on a device before they are stored. The keys that open them are derived from your recovery phrase. The API returns them as sealed blobs, and only a client holding those keys can open them. See Encryption and sealed data.

Start here

QuickstartMake an API key and your first request.

AuthenticationAPI keys, sessions and device credentials.

API referenceEvery endpoint, error code and limit.

Pairing devicesAdd a phone or browser to an account.

What is built

Feature	Status
REST API over accounts, devices, email addresses, messages and billing	Available
Sessions from the recovery-phrase handshake	Available
API keys, Operator plan and up	Available
Device pairing and device credentials	Available
Live signals to paired devices: removal, address assignments and new mail	Available
Folders, stars and a Sent folder	Available
Sending mail with attachments: sessions and devices from Personal, API keys on Scale and up; Free receives only	Available
AI agents through mailcycle-mcp, Scale plan and up	Available
Your own domains, Scale plan and up	Available
Support requests, encrypted end to end	Available
Webhooks, Operator plan and up	Available
Event stream: sessions on any plan, API keys on Operator and up	Available
SDKs for TypeScript, Python, Go, Rust, Swift, PHP, Java, .NET and Ruby	Available
Usage and event logs, in the app and over the API	Available
The encryption format, so you can write your own client	Available