So these are imap accounts. Are they all the same mail provider? Are the filters server based, or Thunderbird based? Please give complete details of at least one of the filter rules

Yes, Wayne, all imap accounts, sorry to have not specified that.

Sorry - I annoyingly repeat a few items following, just for in-stream clarity...

| Are they all the same mail provider?

Multiple mail providers including: 1. Four addresses at one of my own domains at hosting.com, one of which gets the majority of the traffic 2. Two addresses at two more of my own domains at hosting.com, 3. Two more addresses, one each at two more domains at hosting.com 4. Two addresses at an organization's domain I manage at Siteground have their own Thunderbird mailboxes, and 5. Several other addresses at the same domain which resides on the Siteground server forward directly to the main address at my domain at hosting.com * 6. Three gmail accounts

| Are the filters server based, or Thunderbird based?

Hmmm... The filters are all set up in Thunderbird, and I'm not aware of the ability to have them resident on either the server or Thunderbird per se, but the *results* of the filters vary: a (very) few filters actually download messages to Local Folders on my laptop, but since that means I could easily lose those in a hardware crash or update (ignoring backups), most of the filters file messages on server-based folders, of which there are a LOT.

• The rogue Folder BS has now stored messages originating from some or all of the sources listed above. I should add that legit BS-related traffic is focused around traffic generated by the organization's domain hosted at Siteground per 4. above, and forwarded to a server-based folder in the mailbox for the most heavily used address in 1. above. The problem is that Folder BS is now sucking up messages with zero relevance to BS, so my hunch is that this is a Thunderbird directory database glitch, but I only have <50% confidence in the usefulness of that hunch.

| Please give complete details of at least one of the filter rules

Keeping in mind that the rogue Folder BS continues to absorb messages without my active approval since the last version of Filter BS was deleted sometime after 11/14/25, those filters would have had rules along these lines:

√ Match any of the following <From, To, Cc or Bcc> contains bs <Subject> contains bs

Perform these actions: Move Message to <Folder BS> (which is a server-based folder 2 levels below the inbox, with 2 levels of sub-folders within it for annual and monthly filing.)

Also keep in mind that I've searched all the filters for the actual text BS stands for and found no other matches since deleting Filter BS. (That said, I'm not clear that the search function in the Message Filters window searches anything other than the names of the filters...)

I just examined the Filter log, which spans 6/9/25 through today, 1/16/26. The results show that: • "Filter*BS" ran 41 times between 6/16/25 and 10/8/25 I identified enough incorrectly filed messages in Folder BS during that time period to know that I would have been so frustrated with the problem that I apparently deleted that filter and created a new version, with slightly different actions required (no tagging or priority change, just moving the message to Folder BS). • "Filter BS" ran 38 times between 10/17/25 and 11/14/25 Once again, I identified enough incorrectly filed messages in Folder BS during that time period to know that I still hadn't solved the problem by deleting and replacing the filter. And once again, I deleted the filter in frustration, and did not replace it. • Entries including the path to Folder BS appear only 79 times between 6/16/25 and 11/14/25, but there are more than 171 messages in Folder BS between those dates - about double what should be there. • Messages inappropriately filed in Folder BS were received as recently as yesterday, despite the continuing fact that There. Is. No. Filter. Set. To. Perform. That. Move.

I hope that provides some clarity... many thanks for any thoughts you can offer.

John