As a follow-up, I did a test. From a yahoo account, I sent a test e-mail to my Gmail to see where it would show up. 1) It landed in my Web Gmail. 2) I did a "Get Messages" on my 1st PC and it landed along with a few other new e-mails. 3) I did a "Get Messages" on my 2nd PC and it did NOT land in the inbox, nor did the other few new e-mails. OK, so it seems it may be a Gmail issue, in that if the e-mails have been downloaded once to one of the TB installs, it will not download to the other. I'll run the test again but this time I'll do the "Get Messages" on the 2nd PC first. Grrr...how annoying is this.

It seems to me like your problem is really using POP for your emails. As I understand it, POP was never designed to accommodate multiple devices getting or sharing emails from the same server. As long as you only have one device, it works OK. I suspect you are running into issues with POP itself or Google's implementation of POP. If you use IMAP instead, it is designed to sync multiple mail clients with the server. I used POP for many years, leaving emails on the server. However, when I got my first smartphone and wanted to see emails there, also, I switched to IMAP.

I could not find any good way to switch to IMAP without just deleting the old POP accounts and creating new ones using IMAP. However, I saved all the messages in my TB POP folders before deleting them to local folders. I then created the new IMAP accounts. After than, any messages that were still on the server synced up into the new IMAP accounts. Any other ones I could copy from the local folders back into the online folders. Once you have all the messages in any account, they will sync up on all your accounts. I believe you could also probably create new IMAP accounts while the old POP ones are still active, and then copy any messages you want from the old to the new accounts before deleting the old accounts. The bottom line is I suggest you switch to IMAP accounts because that should do what you want.

Thanks for the suggestion, but I have a solution to my issue without having to change my accounts to IMAP. I remembered I had the same problem with my Outlook 2010 accounts on the same machines before Google would no longer allow Gmail to download emails to Outlook 2010, they said it was not secure enough. They needed to mind their own business. it is my Outlook on my machines, not theirs, they should let me worry about security on my machines. Microsoft's interference is bad enough. But now I can abandon using Outlook if I choose to do so, but I keep it around for the historical calendars and e-mails. Unfortunately, I have not found a way to import Outlook e-mails into TBird.

Microsoft products like Outlook 2010 are only supported for a certain length of time, and Outlook 2010 is beyond support. That is one advantage of an open source product like Thunderbird that is regularly updated by its community. I assume you were using Outlook 2010 to access your Gmail account. If you did leave the emails on the server with POP, switching to IMAP in Thunderbird will cause all the past emails on the server to sync to Thunderbird on every device where you are using it. If you prefer to remain with the limitations of POP, that, of course, is your choice. Nevertheless, TB works very well with Gmail and IMAP. So it would be pretty easy to set up an IMAP account in Thunderbird either in a new profile (or fresh install) or even by adding as an additional account to see if it gives you everything you want. If it does, you can keep it. If not, you can always stay with what you have.

Mark, thanks but did you read my reply to your first post? I have fixed the POP problem. BTW, what is involved in a new profile? Is that like having a new account name or what. Too many assume that everyone knows what the terms bandied about mean. In simple terms elsewhere, a profile contains things like name, e-mail address etc.