Cannot start TLS: handshake failure

[ivokamburov]

Hello,

we set up Proxmox Mail Gateway 8.2.0 to relay outgoing emails. This mostly works good (with emails hosted by MS Exchange Online for example), but with certain mail providers (like for example IONOS) outgoing Emails show up in the Deferred Mail Queue with the Reason "Cannot start TLS: handshake failure". Apparently the emails still do arrive at the destination, as we managed to test. Because of this error message we also uploaded a Wildcard certificate and set up a TLS Destination Policy of Destination - * Policy - encrypt

We would really appreciate your help on why this happens and if our configuration is correct.

Kind regards

 

[Stoiko Ivanov]

please share some logs from mails that get deferred - also consider testing if there's an issue connecting to the systems with
`openssl s_client -connect <ip.of.mail.system>:25 -starttls smtp`
(from the top of my head - check with the help-output/man page if it's not working)