What is the size of your Inbox?

What is your anti-virus software?

Hi christ1, thanks for responding and for your interest in helping me out. First, it appears that new e-mail messages are starting to populate my inbox again, and they are again coming in in duplicates. All messages prior to today and dating back to 1/1/2022 are still missing in action. According to the inbox in my profile dated today it contains 7,219 KB of data. I know that it was much larger than this prior to this crash or whatever this event would be called. For example, my "drafts" folder currently says it contains 839,028 KB and there is not one draft in that folder. To answer your second question, I have the MS Defender antivirus which was installed with this version of Windows back on 7/19/2021. It tells me that everything is up to date and no issues have been detected. I assume that it scans my system periodically but I do not generally scan it manually or independently of whatever it does in the background. Thanks again for your effort and assistance.

Each message that comes in arrives in duplicate, requiring me to go through the messages daily and delete every other one.

What's your account type - POP or IMAP?

If POP, are you leaving messages on the server?

It's POP. I haven't logged into the server in awhile but I can do that. My TB settings are set to leave messages on the server for "at most 14 days". Would messages on the server continue to pile up despite that setting? Thank you again for your attention and help on this.

I think we're dealing with two separate issues here.

1. some sort of data loss following mail file corruption

When accumulating messages in Inbox anti-virus software takes a lot longer to scan a large Inbox file. During scanning the file is blocked for Thunderbird, often leading to 'Not responding' situations. It can also cause mail file corruption, which then can cause data loss. This is possibly what happened in your case.

I don't think you can recover any lost messages unless you do have a backup of your Thunderbird profile created prior to the incident.

These are some generic suggestions to avoid problems with anti-virus software.

Create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_how-to-find-your-profile

Don't let your anti-virus software scan incoming and outgoing messages.

Don't let your anti-virus software scan attachments.

Don't let your anti-virus software intercept your secure connection to the server.

Remove any add-ons your anti-virus software may have installed in Thunderbird.

Keep it working. http://kb.mozillazine.org/Keep_it_working_-_Thunderbird

And last but not least, backup your Thunderbird profile on a regular basis. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

For example, my "drafts" folder currently says it contains 839,028 KB and there is not one draft in that folder.

You need to allow Thunderbird to either automatically compact folders, or manually trigger compacting. https://support.mozilla.org/kb/compacting-folders

2. duplicate messages in Inbox

This may be due to a corrupted popstate.dat file. Try to delete popstate.dat. http://kb.mozillazine.org/Popstate.dat

Thank you very much. I will follow those instructions and report back on the status. Have a great day!

Please do post your results. Thanks.

Sorry for the delay. I managed to crash Windows and had to reinstall it, along with all programs, including TB. Major time-consuming PIA. I did find a saved TB profile from a year or two ago so I was able to recover almost all of the archive folders I lost. The basic problem still exists and I am hoping to follow through with that today sometime. I will report back and I appreciate your patience and follow-up.

So you lost your disk? Yeah, sorry to hear that - it's a super PITA. Backups only get you so far.

My apologies to all, especially Christ1, whose efforts and responses are very much appreciated, for the long delay in addressing this problem further. Life distractions forced me to simply live with this problem, until this week when I was able to give it attention again. I did delete the popstate.dat file, which seemed to immediately re-generate itself. Not sure whether that was supposed to happen, but it did not solve the problem. I discovered that duplicate messages began to appear on the server as well and I got through to their support department, which discovered the source of the problem rather quickly and resolved it on their end. I'm embarrassed that it turned out not to be a TB issue, but the duplication of messages didn't show up on the server until now. At any rate, thank you to the support community for all its efforts in my behalf. Joe Rogul