One of my computer’s hard disk didn’t survive a recent power failure so I had to set up its Thunderbird client again (a backup didn’t work, don’t ask). My internal IMAP server uses a self signed certificate which worked like a charm until now. Normally, the first time Thunderbird connects to the server after the account has been set up, it will display a warning for this certificate with an option to permanently accept it. This warning did not come, so no emails were available. The same procedure worked fine for the similarly configured SMTP server, so apparently the feature/workaround for self signed certificates wasn’t removed on purpose.
I found two workarounds for this:
- Start with an older Thunderbird version (102.0.0 worked fine for me) and upgrade to the latest one. Unfortunately older versions seem to vanish from the interwebs within a very short time when a new release comes out (or equally possible my Google Fu has failed me again [it did, here they are]).
- With Thunderbird 102.0.3, in Account Settings -> Server Settings set Connection Security from “SSL/TLS” to “none”, then try to get the emails. All of a sudden the missing dialog popped up, I could accept the certificate and emails started being downloaded. While that was running, I changed the setting back to “TLS/SSL” and all seems good now.
I found this by pure chance because I was desperate enough to completely disable SSL just to get to my emails.
I am posting this so I can look it up later in case I need it again (Google will hopefully turn it up when I search for a solution). But if it helps others too: You are welcome.
I’m sure many people are now itching to suggest other possible solutions. If your’s is “Use Let’s encrypt certificates”, please read the following link on why you might not want to do that for internal servers.