Start with authentication (port 587). If that doesn’t work, check your mynetworks . Nine times out of ten, that resolves the issue.
In this post, we’ll break down why this happens and the three most common ways to fix it. An SMTP relay is when a mail server accepts a message and delivers it to a domain that is not its own. zimbra relay access denied
| Setting | Command to Check | Desired State | | :--- | :--- | :--- | | | zmprov getServer zimbraMtaTlsAuthOnly | TRUE | | Submission Port | zmprov getServer zimbraMtaAuthEnabled | TRUE on port 587 | | Trusted Networks | zmprov getServer zimbraMtaMyNetworks | Only internal subnets | Final Thoughts "Relay access denied" is frustrating because it stops legitimate email. But remember: without this guardrail, your Zimbra server would be an open relay—and it would be blacklisted within hours. Start with authentication (port 587)
It usually appears without warning. One minute, a user or an application is sending mail fine; the next, emails are bouncing back. Don’t panic. This error is actually Zimbra’s security system doing its job—it just needs a little adjustment. In this post, we’ll break down why this