For those who come here: I solved it by commenting out port=0 so that default imap settings becomes available /etc/dovecot/conf.d/10-master.conf:
service imap-login {
inet_listener imap {
#port = 0
}
…
}
I guessed correctly that somehow the imap protocol is being blocked somehow (You should also check the firewall) :)

I face the same trouble .... no way to solve it, i´m try everything over 5 hours

excellent solution. thanks a lot

At first, I thought I was experiencing problem with my configuration. Found this blog, and followed it.

But then I realized, that it is the way that Thunderbird checks for email settings during the first setup. It first checks and connect to IMAP on port 25 then port 143.

Well, in my case, I did not open port 25 and only use port 143 for IMAP, so it would be obvious that whenever Thunderbird checks port 25, it got rejected and made this error shows up in the log, but I do not have problems with authentication nor SSL, so I am just going to leave this like now, because I believe that my configuration is correct.

Here is mine:

service imap-login {
inet_listener imap {
port = 143
}