- In the Gmail app, open Settings → Add account → Other.
- Enter the email address you send protected attachments from, and choose Personal (IMAP) when prompted for the account type.
- On the outgoing server screen, enter the gateway's inbound server settings — server address, port, and your account email as the username.
- Set the security type to match the port (SSL for 465, STARTTLS for 587), enter your password, and finish setup.
- Send a test message from this account in the Gmail app to confirm it routes through the gateway.
This only works for an address added to the Gmail app as a separate "Other" IMAP
account — a real @gmail.com account signed in the normal way always sends through
Google's own servers, with no option to change the outgoing server. If your mailbox
is a real Gmail address, see [Gmail via Google Workspace SMTP relay](/setting-up/gmail-relay)
instead, which routes at the domain level rather than in the app.