It could be due to this one little file.  Excellent work ViruSoul! “HeyThomas,

I think I figured out the solution, its been 9-10 Hrs since I testing it, so far its working good. Here it is what I did … (-:

Quit from Mail.app now …

Go to >> Home> Users > {Your User Account} > Library > Mail … Look for file nameMessageUidsAlreadyDownloaded3, move this file to desktop or whatever location you want …

Now open Mail.app again, this should work properly now (-:

Good Luck.
-Sonu”