Firefox doesn't do email, it's strictly a web browser.

If you are using Firefox to access your mail, you are using "web-mail". You need to seek support from your service provider or a forum for that service.

If your problem is with Mozilla Thunderbird, let us know and we can move this thread to the Thunderbird queue. This question currently is in the Firefox queue for answers.

Duh. I didn't say Firefox, did I? I got to this page through Thunderbird/help. Sorry I didn't make that clear. The comment should have referred to Thunderbird.

I find Thunderbird's junk handling to be a bit erratic.

Most of my junk goes into the relevant Junk folder. Not all of it, so this is a puzzle as to why it is inconsistent. I suspect there are race hazards and when it is busy processing many mails from multiple mailboxes, a process gets interrupted and doesn't correctly resume its task.

However, you can create a "don't care" solution. Use a Saved Search folder to aggregate all messages with Junk status. Then they are presented to you all in one place, and you can delete them all with ctrl+a, then delete, regardless of their actual location. You can also get the Saved Search to encompass Spam folders, so that messages singled out by spam detectors can also be bundled up along with the Junk for quick elimination.

And, in your subject line, you suggest automatic deletion of Junk.

If "deletion" means "move to Trash", all well and good. But mistakes do happen and if messages were permanently deleted just for being labelled as Junk, then you'd most certainly lose some items that you'd have kept, given the choice.

Obviously, I'm not getting my point across properly. My junk mail filters are working perfectly. However, why would Thunderbird automatically put email marked as JUNK in my INBOX instead of the JUNK MAIL FOLDER???? If it clearly identifies the emails as junk, it should then proceed to automatically move them to the junk folder. But NO, Thunderbird just leaves them in my inbox. So I have to go through the process (in each inbox) of going to Tools and Delete mail marked as junk.

My guess is because you have not set up Junk controls. The default action is to mark as junk and leave in the Inbox. This tells you how junk controls work.

http://kb.mozillazine.org/Junk_Mail_Controls