Zimbra Relay Access Denied Jun 2026

To fix the error, you must first understand what "relaying" means in the context of SMTP (Simple Mail Transfer Protocol).

If the client is configured correctly but it still fails, verify that Zimbra's MTA is allowing SASL authentication. zimbra relay access denied

zmprov sp user@yourcompany.com newpassword To fix the error, you must first understand

If your Zimbra server sits behind a firewall, ensure that port 25 (SMTP) is correctly forwarded. Sometimes, a firewall performs "loopback NAT" issues where internal users cannot reach the public IP, but external users can. For external senders getting Relay Access Denied, ensure the firewall is not modifying the SMTP transaction in a way that strips headers or authentication. To fix the error

If local mail is also being rejected, your domain might not be recognized.