17.03.22, 08:05 +0100, Jeremy Ardley:
I've been using Thunderbird for years now but made some minor tweaks as I'm setting up an imap proxy for remote access to my debian/dovecot/postfix server. The issue is I changed the account settings in thunderbird to use STARTTLS and port 993. It now doesn't work. I see a connection in wireshark, but then nothing happens and dovecot logs no attempt to authenticate and it just times out.
By default, Dovecot listens on port 993 in TLS wrappermode, i. e. the encrypted connection has to be established before any user data can be transmitted (nothing will be sent unecrypted). OTOH, by telling Thunderbird to use STARTTLS you told it to try to establish an unencrypted network connection first, and afterwards issue the STARTTLS command over this plaintext connection to start the encryption.
This won't work. Change the connection security in TB to SSL/TLS. -- Regards mks