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Guides

Gmail (via Google Workspace SMTP relay)

Route a Google Workspace mailbox's outgoing mail through the gateway.

If your organization sends through Google Workspace, add the gateway as an SMTP relay service in the Google Admin console rather than in individual mailboxes — this applies the setting to everyone sending from your domain.

  1. In the Google Admin console, go to Apps → Google Workspace → Gmail → Routing.
  2. Under SMTP relay service, add a new setting.
  3. Enter the gateway's inbound server settings as the relay host and port.
  4. Choose an authentication method that matches how your account was set up — your gateway account's own email as the username, with whichever credential type your account uses.
  5. Save, and send a test message from a Workspace mailbox to confirm it's routed through the gateway.
This changes routing for outgoing mail from your whole domain, not just one mailbox — if you only want to protect attachments from specific senders, configure the gateway per mailbox in each Gmail account's own SMTP settings instead.