ZeptoMail + Gmail send-as

Prerequisites

  • Domain on Cloudflare (or DNS you control)

  • Cloudflare Email Routing (or other MX) for inbound

  • ZeptoMail account with Mail Agents available

Steps

  1. In ZeptoMail, create a Mail Agent per project/domain silo.

  2. Add and verify the domain; publish SPF/DKIM (and any CNAMEs) via Cloudflare — prefer managing those records in the org infra Pulumi stack.

  3. Invite collaborators with Agent-level access (Postmaster / Engineer / Viewer as needed).

  4. Generate a separate SMTP key per person (never share a "master" password).

  5. In each user’s Gmail: Settings → Accounts → Send mail as — SMTP host/port from ZeptoMail; username/password = that user’s key.

  6. Confirm "Treat as an alias" only if you understand threading implications; it does not fix DMARC.

SPF / multi-user

SPF and DKIM are domain-level. One correct DNS set authorizes all users of that SMTP provider. Volume and auth caps are account-level — create per-user keys and watch shared quotas.

Do not

  • Activate SMTP IP allowlisting if Gmail (dynamic egress) is the client — it will break send-as.

  • Hand everyone one shared SMTP password.

  • Point human mail through Resend "because the app already uses it."

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