When I started Thunderbird today, it opened three windows. Each window was identical. I closed two of them and then quit Thunderbird. As soon as I started Thunderbird, I had three windows again.
I found a Mozilla bug report from 2015 that had some tips for getting the additional windows closed. Choose one of the open Thunderbird windows and select Close from the File menu. Do not use ALT-F4 or CTRL-W to close the window.
I talked about the joys of running my own mail server last week only to find that my mail server was broken yesterday. Spamassassin stopped doing DNS lookups for RBL and SPF checks. I had one of these moments:
My logs looked like this: plugin: eval failed: available_nameservers: No DNS servers available! plugin: eval failed: available_nameservers: No DNS servers available! rules: failed to run NO_DNS_FOR_FROM RBL test, skipping: (available_nameservers: [.