Fix the Gmail "Send mail as" error "Functionality not enabled" in Google Workspace

When you set up "Send mail as" in Gmail, you enter your name and email address. Sometimes Gmail then shows this error message:

Functionality not enabled.

You must send through gmail.com SMTP servers when you send as someuser@gmail.com.

However, this functionality is not available for your account. Please contact your domain administrator for more information.

This error usually occurs when you add a personal email address (…@gmail.com) or a Google Workspace email address on your alias domain (…@aliasdomain.com).

A Google Workspace administrator for your domain must change a Gmail setting. Do these steps:

1. Sign in to the Google Workspace Admin console at https://admin.google.com/.
2. Go to Apps > Google Workspace > Gmail.
3. Click End User Access.
4. Click Allow per-user outbound gateways.
5. Select Allow users to send mail through an external SMTP server when configuring a "from" address hosted outside your email domains.
6. Click Save.

Note: This change can take up to 24 hours to apply to all users. If the error continues, wait until the next day. Then set up "Send mail as" again in the usual way.

If you need help, send an email to support@itsolver.net or phone 07 3123 6000.