Maximum capacity of a Thunderbird account?

I know someone who has lots of emails in a Thunderbird account. One day Thunderbird stopped receiving emails and asks the user to either delete or compress old emails to make more space. Unfortunately, due to the large number of incoming emails Thunderbird got "full" again.

So, is there a cap on the size of a Thunderbird account? Is there a way to lift the cap? There is still a lot of room left on the hard drive.

Solution 1:

There is a limit of 4GB (in some instances, only 2GB) on a folder:

http://kb.mozillazine.org/Limits_-_Thunderbird#Folders_and_messages

There is apparently no way to lift the cap other than to "configure the mail directories and/or the Local Folders directory to be stored outside of the profile", as in the link.