A bit of an update, I hope this may help. I went and look at "the 449th" message on the mail server. That message has a 20M attachment. Deleting this message, nor its attachment, is not an option. This is also NOT a unique situation as many of other messages also have large attachments as well.

Did the 449th message fully download successfully?

It stopped at 448. Have tried many times, but it just keeps saying "Downloading message 1 of xxxx," but never finishes message 449 or goes any further.

Pease do keep in mind that "message 449" might NOT necessarily be the cause that is preventing me from retrieving the rest (bulk) of my messages on the server. "Message 449" only served as an "interesting observational fact." It was simply the next message that was on the the list, according to the date of the last downloaded message.

FYI, everything is left on pop3 default but for "Leave messages on server" "For at most xx days," which I unchecked, and I also redirected the Local Directory to a "Thunderbird\mail" directory under my users directory instead of default weird, hard to remember, and very forgettable directory chain under "AppDate\local\..." when doing backups and other maintenances.

Would I lose any of my messages if I was to setup and THEN DELETE an imap email client to this email account? I just want to see if Thunderbird would successfully download all my messages under an imap client.

Why are you setting up your account over again?

HI Matt,

Please reword. I did not understand your question.

If I had to hazard to guess, I would think that you have misread my last paragraph. What I would like to do, as a test, is to setup Thunderbird to access my mail server via imap protocol instead of pop3. This is just to see if Thunderbird would address my emails in totality or will it also stop at a certain point. Either way, I would like to remove the imap client after the test. The question here is, will deleting the imap client in Thunderbird also delete all my messages on the server for this email account?!

Do you really need to use POP rather than IMAP? If POP won't let you download what you need, maybe the way forward is to set up as IMAP, and then convert to POP: https://support.mozilla.org/en-US/kb/faq-changing-imap-pop