Sometimes when I download messages the body is corrupted and I receive part or all of the body of a different email
I upgrade to Windows 8.1. Now messages are corrupted sometimes. I receive the body of the wrong message - several messages will have the wrong content, sometimes across email accounts.
I had no issues with Windows 7.
Opaite Mbohovái (4)
Sounds like you need to do some file maintenance. Right click the problem folder and select Properties. Then Repair Folder. It will try to recover any messages still recoverable. Then read this. http://kb.mozillazine.org/Keep_it_working_%28Thunderbird%29
I am still having these issues. I have now moved to an SSD that I was using for Windows 7. The issue occurs on multiple accounts. The problem is becoming worse. Repair the folder causes duplicate message, and only a few of the missing ones.
so the underlying message store is corrupt if messages and duplucating
This will cure the corruption but may well see mail simply disappear in the process.
Right click the folder and select compact.
What anti virus are you using?
Tried it all. I am using Forticlient. I have cleaned out my emails, turned off filters, etc. I am trying to exclude the folders on AV for a test.