My environment:
- ubuntu 20.04.1 LTS
- postfix 3.4.13
- dovecot 2.3.7.2
Setup is extremely simple. I configured postfix via built-in master as an internet site host. Dovecot (I use it as IMAP server) settings are all default. Now, I'm able to connect to this server with any mail client at my hands (outlook, eM Client) and do routine mailwork except Thunderbird.
When I try to setup my account in Thunderbird I got such window for infinity:
On server side I see these suspicious entries in mail.log whenever I try to test my settings in thunderbird settings windows (test passes OK):
postfix/smtpd[13695]: improper command pipelining after EHLO from me.example.com[192.168.1.25]: QUIT\r\n
postfix/smtpd[13695]: disconnect from me.example.com[192.168.1.25] ehlo=1 quit=1 commands=2
I specifically simplified this setup because I have a fully fledged mail server with authentication, SSL, DKIM, etc. but I'm also unable to use thunderbird with it (behavior is exactly the same).
I'm out of ideas how to make thunderbird to connect to my server. Any help is appreciated!
Best Answer
Configure your Thunderbird to use the TLS-secured ports, behaviour with your test is likely not "exactly the same".
The log you show in your question for your simplified test likely says little about the actual problem you are attempting to diagnose.
The thunderbird connection test simply disconnects after not being offered secure authentication by the SMTP server on port 25. This is not unusual with the settings in your screenshot. Port 25 is used for receiving internet mail from other servers. Typically you would only offer authenticated submission on port 465, secured via TLS (and IMAPs via port 993, also secured via TLS).