Please read this: Keep it working - Thunderbird

11,000 messages in any folder would be difficult for any program to manage effectively. I'm not surprised that there is a problem. As you stated, it took 45 minutes for them all to be counted.

I advise using webmail to sort those messages into other folders, perhaps by yearly or monthly archives. Don't have Thunderbird running when you do this. When finished the sorting, then run Thunderbird so it will update the IMAP folders, and make sure you have all of them subscribed.

Bruce A. Johnson said

Please read this: Keep it working - Thunderbird 11,000 messages in any folder would be difficult for any program to manage effectively. I'm not surprised that there is a problem. As you stated, it took 45 minutes for them all to be counted. I advise using webmail to sort those messages into other folders, perhaps by yearly or monthly archives. Don't have Thunderbird running when you do this. When finished the sorting, then run Thunderbird so it will update the IMAP folders, and make sure you have all of them subscribed.

Bruce:

It appeared to take about 45 minutes to download all of them after I created the account. The counter showed that it had received the 11,000 emails and the resulting file size is about 1.5 GB. Shouldn't I be able to see them all? I can see how it could be challenging to parse a 1.5 GB size file. Did I exceed a limitation? As an aside, my ISP daily usage statistic reflected the download size. This is part of a host migration and I've pointed the MX record to the new host, though the old host account is still active. Thank you.

I suggest that the emails are no longer in Thunderbird.

Your anti virus activated and did what? The usual automatic cure is to completely delete the file that holds the inbox emails. so if you had 10,000 email in the box, it will delete the whole lot.

So perhaps you need to start again and turn of the email scanner so it does not delete all your mail.

Just my guess. What does your anti virus log show it did?

The Avast "Quarantine virus chest" shows that it captured 3 emails that contained viruses. According to the Thunderbird properties for the Inbox, it only shows a total of 610 emails and a space of about 80MB. But, Windows 7 is reporting the size of the Inbox file to be 1.5 GB. Perhaps, the anti-virus corrupted the file during the download.

For Thunderbird, there is the theoretical message limit of 4 billion messages in a folder, but for practical reasons, the limits are much lower. There is a practical limit of 4 GB for a folder because in Thunderbird, all e-mail messages in a folder are stored in a single "mbox" file. See this article for this info

Now, you are using IMAP which traditionally doesn't save the messages on your computer, but if your settings in Thunderbird for the e-mail account are to "Keep messages for this account on this computer", then you can encounter problems. Like the index for the folder getting corrupted, or the mbox file on your hard drive gets corrupted.

Thunderbird menu: Tools: Account Settings. Select "Synchronization & Storage" under your e-mail address on the left. This setting is on the right.

The Inbox is the most used folder, with e-mails going in and out of it constantly. All the e-mails in a folder are in one file (mbox file), on your hard drive. When a message is deleted from the folder in Thunderbird, the index for that big file is updated, but the file itself will still contain the deleted message until the the folder is "compacted".

So the Inbox is the most vulnerable to errors like the index for it being corrupted or the mbox file getting corrupted on the hard drive.

When you keep 11,000 messages in the Inbox, the probability of errors goes up exponentially.

So to solve your issue, please follow the advice I gave. Quit Thunderbird, use webmail to sort those 11,000 e-mails into other folders. Then run Thunderbird and make sure the IMAP folders for your account are updated and subscribed.

Then from now on, try to keep your Inbox as empty as possible.

Also, read and follow the other advice in the article Keep it working - Thunderbird. Your response doesn't mention if you even looked at it.

The 4Gb limit technically does not apply to IMAP folders. That was one of the last things Ludo did before he went to Google.

Some know Avast issue here https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#AVAST

Given Avasts track record with Thunderbird, corruption is a very really possibility.

Matt said

The 4Gb limit technically does not apply to IMAP folders. That was one of the last things Ludo did before he went to Google. Some know Avast issue here https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#AVAST Given Avasts track record with Thunderbird, corruption is a very really possibility.

Matt:

At this point it does appear to be a corrupt file because I've pointed the domain back to the old host, turned off the anti-virus and watched the files download. I also watched the Inbox size grow in windows explorer, yet the messages still don't appear in the Inbox. I have since moved all of the readable messages to another folder for safe keeping. How can I now delete the corrupted Inbox file and start anew? Thanks.

Bruce A. Johnson said

...... Also, read and follow the other advice in the article Keep it working - Thunderbird. Your response doesn't mention if you even looked at it.

Bruce:

Yes, I did read the article, which is why I'm now focusing on the possibility that the Inbox file is corrupted. Thanks.

2TallinVA said

At this point it does appear to be a corrupt file because I've pointed the domain back to the old host, turned off the anti-virus and watched the files download. I also watched the Inbox size grow in windows explorer, yet the messages still don't appear in the Inbox. I have since moved all of the readable messages to another folder for safe keeping. How can I now delete the corrupted Inbox folder and start anew? Thanks.

Are you another of these folks that has changed email hosts and failed entirely to comprehend what synchronize means?

You can not use IMAP account to hold your mail while you change email hosts. When you connect to the new server, Thunderbird commences to synchronize. The first thing it does is delete everything it downloaded from the old host because it is not on the server anymore. That is a reality of IMAP.

At this point it is difficult to advise what to do, other than press F10 to make the main menu bar visible, then choose compact from the file menu. I really do not know what will happen. The file will certainly shrink. your new batch of email may become visible at the same time. Or they may be gone as well if there is corruption.

Once you have your mail stabilized. install the import export tools add-on https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

Use the tools to export all the mail in the account as MBOX files and reimport them to Thunderbird local folders. Make a folder in Local folders, select it and right click to importexporttools

Only when you have exported the mail and then imported the mail will you be in a position to change hosts, at which time the mail in your account will disappear again (Good thing there is a copy in Local Folders) and you should compact the folders again to shrink the mail folder files.

Matt:

That's good information on how synchronization works. I'll keep that in mind when I switch back to the new host. However, this problem first appeared after having downloaded the items from the old host but before connecting to the new host.

Is their a way to simply recreate the Inbox? Is compacting my only option? The downloaded messages have been moved safely to another folder, so I'm not concerned about losing anything at this point. BTW, Thunderbird warns me that I have reached 100% of my email storage quota on the host, but that shouldn't affect my ability to download and view the mail in Thunderbird.

Matt:

The compacting seems to have done the trick. The Inbox went from 1.8 GB to 0kb. All folders now seem to be syncing with the host. Anti-Virus protection is still disabled. I'll came back and share the results. Thank you.

Well, it didn't work. It downloaded all 11,000 + files to the temporary folder I created, but still will only show 164 messages even though both Thunderbird and Windows Explorer both shows a file size of 1.4 GB and Thunderbird shows over 11,000 messages in the new folder.

It appears that it will only show the emails that it thinks are unread.

I hope that is the case. Press F10 to make the main menu br visible if it is not. Select view from the menu then messages and ALL.

Matt said

I hope that is the case. Press F10 to make the main menu br visible if it is not. Select view from the menu then messages and ALL.

Matt:

Would that be View, Folders, All? Thanks.

Whoops! Posted to wrong thread.