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Email Signatures API

Email

Added

Section titled “Added”

  • Signatures API — New endpoints to create, list, retrieve, update, and delete HTML email signatures per grant. Each grant supports up to 10 signatures for different contexts (e.g. “Work”, “Personal”, “Mobile”).

    • POST /v3/grants/{grant_id}/signatures — create a signature
    • GET /v3/grants/{grant_id}/signatures — list all signatures for a grant
    • GET /v3/grants/{grant_id}/signatures/{signature_id} — retrieve a single signature
    • PUT /v3/grants/{grant_id}/signatures/{signature_id} — update a signature
    • DELETE /v3/grants/{grant_id}/signatures/{signature_id} — delete a signature

  • signature_id on send and draft endpoints — Pass a signature_id when calling Send Message, Create Draft, or Send Draft. Nylas appends the signature HTML to the end of the email body at send time, including after quoted text in replies and forwards.

  • Cross-provider support — Signatures are stored on Nylas, not on the email provider. A signature you create once works the same across Gmail, Microsoft 365, and all other supported providers.

  • HTML with sanitization — Signature content is HTML with full control over formatting, links, images, and layout. Nylas sanitizes HTML on input to prevent unsafe content. Images must use external URLs (no base64 inline). Maximum size is 100 KB per signature.

For full details, see the Email Signatures documentation and the Signatures API reference.