I cannot solve the issue, but I'll share a possible cause. I presume this is a POP account. If so, there is a file named popstate.dat in the profile folder that keeps track of last downloaded message to prevent what you are describing. Now, if some process is running (antivirus?) that is preventing thunderbird from saving that file, then it never updates and keeps downloading the same messages. If you check in profile folder, in the Mail folder for the account, you will see the file. To get there: - click help>troubleshootinginformation, scroll down to 'profile folder', click 'open folder', exit thunderbird. You are now in the profile. Click the Mail folder and then the account folder to see the popstate.dat file.

Found the Mail folder. Opening has one option. a folder called, Local folders. Their is no account folder? I use Norton 360 security. If I can show them this issue, they may fix it? I'm rather computer illiterate.

POP accounts are not my strength, but if you post screenshot of the Mail folder and of the Local Folders folder, either I or another may have suggestions on this.

adding this to the last comment Just tried %APPDATA%\Thunderbird\Profiles\ Message says "No Items match your search"

here's a screenshot. Not the file path on top. I afraid if I can't fix this, it will wear out the digital harddrive

please post screenshot of the inside of Local Folders. If there is an account folder, do a screenshot of its contents. You will possibly see entries such as inbox, sent, draft,etc. also check the Mail folder.

On your earlier post, entering %appddata% alone on the search bar on desktop brings up appdata\roaming. Entering the other characters is not needed. That suggestion is often provided as many users do not know how to locate appdata\roaming\thunderbird

First, the local folders folder is inside the Mail folder. If you click on the previous screenshot you will see that inside the mail folder, the only folder is the local folders. I'm attaching a screenshot of the contents of the local folders C:\Users\Steven\AppData\Roaming\Thunderbird\Profiles\y2bnlhxs.default-esr\Mail\Local Folders

I am struggling to figure out where your other account files are. Try this: highlight the inbox for the account, rightclick and select properties . Then click to that location in windows file explorer and do a screenshot. That may show us the inbox and popstate.dat file.

Here is a screenshot. It appears to be on the google email website?

Aha. I had been presuming you had a POP account as your description of problem mirrors a common POP problem. Since this is IMAP, the account is attempting to sync with the PC. My assumption (and it's nothing more) is that your account takes a long time to download. What you might try is click to the synchronization&storage pane for the account and change the sync setting to just the last 30 days.

As I said earlier, Not that computer literate. Thanks for your time and interest. Much appreciated. I'll see if this works. Appears to do the trick.