#1 OutOfMemoryError: Java heap space

[Anonymous]

Error popup (in German):
Der Ordner konnte nicht vollständig Synchronisiert werden
java.lang.OutOfMemoryError: Java heap space

I have quite many folders and they are full of mails (a few thousand all in all). On the other hand, I have 2 GB od RAM. Maybe I should just start the Java VM with other memory parameters?