client network socket disconnected before secure tls connection was established

gsnick

Hello,
We are sending emails from reachinbox.ai through mailcow, port 465, and we see errors like “client network socket disconnected before secure tls connection was established”.
Had anyone encountered such issues and knows how to fix them?
Are they caused by mailcow server?
I will be grateful to any help or hints how to fix this.
Thanks you.

esackbauer

Looks like you set up your mailcow with the wrong connection details in reachinabox.
Please try port 25 with STARTTLS.
Seems like you are trying an unencrypted connection (e.g. with STARTTLS which starts unencrypted) on port 465.
That port needs a TLS/SSL connection rightaway.