Gmail Send-as via Blindrelay SMTP

Send from a verified Blindrelay domain while composing in Gmail — or use the same SMTP settings in Apple Mail, Outlook, Thunderbird, and similar clients. Blindrelay authenticates your API key, signs DKIM, and delivers against the same monthly quota pool as POST /v1/send (SMTP size-based units below). Requires Mini or higher.

SMTP settings

• Host: smtp.blindrelay.app
• Port: 587 (TLS / STARTTLS)
• Username: apikey
• Password: an API key with the send scope (create on API Keys (sign-in required) )

Gmail setup

1. Ensure the From address uses a Blindrelay domain that is verified (SPF + DKIM + DMARC).
2. Make sure that address can receive mail (Gmail sends a verification message). Cloudflare Email Routing to your Gmail inbox works; Blindrelay does not need to host the mailbox.
3. In Gmail: Settings → See all settings → Accounts and Import → Send mail as → Add another email address.
4. Enter your name and the Blindrelay address, then choose to send through Blindrelay SMTP with the settings above.
5. Confirm the verification email Gmail sends to that address.

Google Workspace

Admins may need to allow users to send mail through an external SMTP server under Apps → Google Workspace → Gmail → Advanced settings.

Limits

One recipient per message. SMTP allows up to 10 file attachments and about 10 MB total message size (10,240,000 bytes; inline images do not count toward the attachment limit). SMTP quota: 1 unit per started megabyte of the message (headers + body + attachments); a 3 MB send costs 3. REST POST /v1/send html and text stay capped at 1 MB; paid plans can also attach files there, at the same per-megabyte rule. Free plan remains REST-only.

Also see the API reference, the SMTP (sign-in required) page, and the API Keys (sign-in required) page.

Ready to send?

Gmail Send-as needs Mini or higher and a verified sending domain. Start free, verify your domain, then upgrade when you are ready to send from Gmail.