So after trying out I figured that after a few weeks my Thunderbird would be stuck after half an hour of usage: And after a bit of Googling I found out this is the common behaviour as if your mail db grows too big you are out of luck, so according to their FAQ even, they say to fix Fix slowness, crashing, error messages and other problems by either rebuilding the database (which only gives you a few minutes in which you can use the program again until it reaches the point where the too many of the emails are about to be re-indexed and then it freezes on you again.