Error sending letters

[Evgeny Glazunov]

Hello!

Please help me at my new job, I got a zabbix ubuntu server and sending notifications via postfix.
Before that, it sent notifications via mail regularly, then it stopped and falls into the SSL connect error: error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol.
Changing ports and various alert settings does not help.
The login and password settings are correct because I can log in through the web page.
Please tell me where could be the problem.

[vladimir_lv]

It's telling you there's a problem with the certificates.

You can try to manually connect to see what's what:
openssl s_client -connect <IP>:<PORT> -starttls smtp

[Evgeny Glazunov]

Thank you very much for your answer, the problem turned out to be on the side of Postfix, since other services tied to sending mail through it also fell off. We solve the issue with certificate chains there.