Upload Attachment

UploadAttachment uploads an attachment POST /api/v1/compose/attachments

Authentication & compatibility

Use a scoped bearer API key with email:send. The key is bound to its user and organization.

Primary SES compose workflow. Reply/forward contexts use public SES mailbox UUIDs; draft and attachment operations use owned records. In legacy non-SES configurations, sending can fall back to JMAP.

Contract 2026-10-04. Your running instance's /api/v1/openapi.json is authoritative for its deployed release.

Request

Set MAILAT_BASE_URL to your instance origin (without /api/v1) and MAILAT_TOKEN to an appropriate credential. Replace path placeholders and example data before running. These examples do not execute in this page.

curl --request POST "$MAILAT_BASE_URL/api/v1/compose/attachments" \
  --header "Authorization: Bearer $MAILAT_TOKEN" \
  --form 'file=@/path/to/file' # Add the required fields listed below

Build the request from the schema below; request.json and upload paths are local placeholders.

Responses

HTTP statuses and body shapes below come from the pinned contract. Not every shared error applies to every request. Retain the original idempotency key when retrying a send.