The current version of Thunderbird 184.108.40.206 has a major bug that causes some mail that is downloaded from the server to disappear in the email client. Thunderbird displays the number of new mails that is in a folder correctly, but when you click to open that folder, the new mail that should be there is not listed in it.
The first time I have read about this message was on the mozillazine forum where a user named soulek described the problem that he encountered after he upgraded the email client to Thunderbird 220.127.116.11.
One solution would be to downgrade Thunderbird 18.104.22.168 to a prior version which should fix this immediately. A better solution would be to download a nightly build of Thunderbird and use that. The bug was fixed and all coming nightly builds should contain the bug fix as well. The most recent nightly build for example contains the fix.
Thunderbird 22.214.171.124 which will include the fix will most likely be released sometime in December which means the only way to fix this bug now is to either downgrade or install a nightly build.
You will have to do the following no matter if you downgrade or install a nightly build:
- Backup your Thunderbird profile folder which is located C:\Documents and Settings\your username\Application Data\Thunderbird\Profiles\random.default (note may vary depending on your operating system)
- Uninstall Thunderbird.
- Go to the Thunderbird profile folder and delete every msf file. Don't worry,Thunderbird will rebuild them once you click on such a folder in Thunderbird.
- Install Thunderbird 126.96.36.199 or the nightly build
The missing mail should appear. Everything seems to have reverted back to normal for me using the above nightly build. Let me know if you encounter errors or if this method is not working for you.
Update: The MSF files that you are deleting are index files that do not contain the mails, just information about them. If Thunderbird cannot locate them, it automatically creates them anew on the system.