I have Thunderbird 102.9.0 (64-bit), running on Linux Mint 20.3 (Una). Thunderbird is losing rules in a message filter, and losing message filters. I have 6 filters, 5 active. I'm getting unwanted emails from 99 email addresses. I created a message filter, "loanfrontends", and added some of the email addresses. As another came in, I would add it. (I'm tracking them in a spreadsheet.) I had 20 rules entered (to move messages containing any of the email addresses to Trash). Ran the filter manually, messages went to Trash. Over several days, more were moved to Trash. Then they weren't. I checked and message filter loanfrontends had only 3 rules. The other 17 disappeared. Concerned that there may be some limit to the number of rules, or filters, or whatever, I created another message filter, "loanfrontends01". (By create, I mean copy loanfrontends, removing existing rules, and adding new ones) I added 4 rules. Manually ran to test, and the messages were moved to Trash. A few days later, I noticed messages not being moved. Checking message filters, I note that loanfrontends01 is gone. I've created another message filter, added some addresses to it. And it also disappeared after a few days. So... why are message filter rules and message filters disappearing?