Sending emails

Attachments

Send files as base64 content or a public path URL. Up to 40 MB per email.

"attachments": [
  { "filename": "invoice.pdf", "content": "JVBERi0xLjcK..." },
  { "filename": "logo.png", "path": "https://example.com/logo.png" }
]

Scheduling

Pass scheduled_at as ISO 8601 or natural language, up to 30 days ahead:

{ "scheduled_at": "in 1 hour" }

Change the time with Update Email, or stop it with Cancel Email.

Batch

Send up to 100 different emails in one request with Send Batch Emails.

Tags

Attach { name, value } labels. They're included in every webhook for that email, so you can match events back to your users or campaigns.

Idempotency

Send an Idempotency-Key header. If you retry the same request (e.g. after a timeout), you get the original email back instead of a duplicate.

Idempotency-Key: welcome-user-123

Custom headers

"headers": { "X-Entity-Ref-ID": "order-981" }