Fastmail API
Fastmail mailboxes, with JMAP on the roadmap
Fastmail
How an account links
- IMAP/SMTP
- emailList mail · Send mail · Drafts · Folders and labels · Threading · Attachments6
- platformWebhooks1
What Aux0 does with Fastmail
7 capabilitiesFastmail mailboxes, with JMAP on the roadmap
Connect a Fastmail account with an app password and get the same unified mail endpoints. Fastmail's own JMAP API is the faster path and Aux0 will move to it behind the same endpoints, with no change on your side.
- List mailPage through messages with search, label and date filters.
GET /v1/emails - Send mailSend a message, reply in thread, or forward one.
POST /v1/emails - DraftsCreate, update and delete drafts in the user's own mailbox.
POST /v1/emails/drafts - Folders and labelsList folders, and move or label a message.
GET /v1/folders - ThreadingGroup messages into threads with a stable thread id.
GET /v1/emails?thread_id= - AttachmentsUpload outbound attachments and fetch inbound ones.
GET /v1/emails/:id/attachments/:attachmentId
Platform
- WebhooksSigned delivery of every event, with replay and a dead letter queue.
POST /v1/webhooks
How an account is linked
AuthIMAP/SMTP
Host, port and credentials for a mail server. For self-hosted mail, regional providers and the long tail that will never ship an OAuth app.
Whichever method a provider uses, your users complete it on a page Aux0 serves under your branding. You receive an account id and a webhook; no password, QR scan or one-time code ever reaches your product. How hosted auth works.
What it is bought for
Use casesTeams on Fastmail rather than Google or Microsoft
What you should know first
LimitsThe constraints, before you commit
These are the provider's rules, not ours. We would rather you read them now than discover one in production.
App passwords are created per integration in Fastmail's settings.
Next
RelatedConnect Fastmail on the free plan
One connected account, every provider, forever. It is enough to build the whole integration before you pay for anything.