The word Bulk says you are dealing with not only Thunderbird, but the yahoo spam filter which has no opt out.

So do these messages fave a coloured flame icon when you look in the bulk folder, or is it the standard grey outline. I ask because thunde4rbird spam filter/ junk controls mark messages as junk and they show up with the orange colour. Yahoo when they put mail in there don't mark it as junk and it remains without the coloured fill.

The importance is that before you can look for solutions you need to know which entity is putting the mail into the folder. My experience is most folk that complain about a bulk folder spam have a problem with yahoo, not Thunderbird.

Using aol mail

Using aol mail

That is Yahoo as is Verizon mail. Verizon recently sold all the properties to Apollo Global Management and they are all to be named Yahoo

See https://www.businessinsider.com.au/verizon-sells-aol-yahoo-to-apollo-global-management-5-billion-2021-5

I had some solution solving this by logging into the Yahoo server online (where I can also see my mail) and moving email that it had placed in Bulk or Spam to my online Inbox folder. I also made sure that I saved the addresses as contacts in there too. If Yahoo decides something is spam, then it seems to be sent to your Thunderbird program already in the Spam (or Bulk) folder. Doing this seems to train Yahoo about what is, and isn't, spam. You may have to do it a few times for it to take.

I'm using aol and have just one family email that gets dumped in Bulk Mail. Why?

I'm using aol and have just one family email that gets dumped in Bulk Mail. Why?

First recall you only use AOL branded email. It is Yahoo, along with their brain dead spam filtering and "Bulk Mail" folder.

Add your family member to your online address book with AOL/Yahoo and the issue will almost certainly stop happening.