a. I then select "Get Messages" for "Myemail", and I see one, or more, email documents found, and begin receipt.
   b. When the receipt concludes, I open "Myemail" Inbox, only to find nothing there. I wander through the entire "Myemail" definition(s), only to
        find that any/all email receipt(s) for "Myemail" have disappeared.

My problem is bigger than just this, but I'll begin here. 1. Sometimes, when requesting "Get Messages" from a Thunderbird account, I will see a message count appear, download, and then conclude. 2. However, when looking through the email inventory for this account, no email appears. 3. IOW. If I have "Myemail" defined, and I'm ABSOLUTELY sure that "Myemail" is entirely empty. a. I then select "Get Messages" for "Myemail", and I see one, or more, email documents found, and begin receipt. b. When the receipt concludes, I open "Myemail" Inbox, only to find nothing there. I wander through the entire "Myemail" definition(s), only to find that any/all email receipt(s) for "Myemail" have disappeared. This is an infrequent occurrence, but does occur. But, the real problem is the synchronization between a specific Thunderbird email account(i.e. "Myemail"), and what a product called "YOTA email migrator"(https://yotasoftware.com/thunderbird-migrator/) says about the current contents of "Myemail". Obviously, the discrepancies are varied, but there will usually be some kind of discrepancy in reporting an "inbox", "sent", "trash", etc. discrepancy. I never keep my email collective permanently in my Thunderbird definitions. My Thunderbird account definitions redefine ALL message repositories from the default (C:) definitions to another (Q:) residency, permanently mounted external drive. So, by the end of my day, my Thunderbird email inventories have all been drained/distributed to other more topic related final storage. I've been a long time Thunderbird user, except during the time when Tbird was struggling with many definition changes for POP3 access. But, I've returned to Tbird now that the smoke has apparently cleared. But, this is my FIRST use of the "YOTA email migrator", which was acquired for use during a "Mailbird" usage, while Tbird was being rebuilt. If you install this "YOTA email migrator" product on your Tbird system, I'm sure you will experience the Tbird email (sub)directory discrepancies that I am describing. I've learned that because my Tbird directories are always zeroed by the end of the day, I can simply erase all those "Local directory" definitions, and they will be rebuilt upon the next Tbird initialization. At which time, the Tbird/YOTA director(ies) content representation will be equal at zero. But, as Tbird email content begins to arrive, and be saved, moved, deleted, etc. the message directory representations between Tbird, and "YOTA email migrator" begin to drift apart. I KNOW this explanations are quite complex, but I think it will become quite clear if you install the "YOTA email migrator" product, and then begin to review the eventual discrepancies between Tbird's message inventory(ies), and that reported by "YOTA". Thank you, very much. And, I'm usually frequently available if desired. Gary Walker - twf6714@outlook.com - https://support.mozilla.org/en-US/questions/new/thunderbird/form