IMAP SSL Issues over Exchange 2016

Infos:

  • Used Zammad version: 5.0.x
  • Used Zammad installation type: source
  • Operating system: Ubuntu 18.04.4
  • Browser + version: Chrome Version 99.0.4844.84 (Official Build) (64-bit)

Expected behavior:

IMAP Inbound and Outbound able to connect to Exchange 2016 IMAP Account

Actual behavior:

Able to connect inbound with SSL port-993.
But cannot connect outbound (SMTP) port-465 with error:
“SSL_connect returned=1 errno=0 state=error: wrong version number”

Steps to reproduce the behavior:

  1. At Zammad Settings → Channel → Email, add new Email Settings
  2. Choose “Expert” mode
  3. Inbound Settings:
    Enter Organization Name, Email Account, Destination Group, Type=IMAP, Host=Mail Server FQDN, User Name, Password, SSL/STARTTLS=Yes, Port=993
  4. Outbound Settings:
    Choose “SMTP - configure your own outgoing SMTP settings”
    Enter port-465
    Click Continue
  5. Error prompt as above screen.

I managed to setup SMTP outbound using Port-587.
From Exchange Server side, have to sacrifice (to disable) TLS.