my outlook for mac 2011 (Version 14.3.8) reacts very slowly while writing or receiving mails. I type something and nothing happens for 10-15 seconds (only the wheel is running). Then the characters appear. That  happens every 30 to 60 seconds.

I already tried it with a new identity. Didn't help.

Emptied the trash. Didn't help.

I use an exchange account and have subfolders in this account

the activity monitor shows high datatransfer-rates (outgoing)

the van of the macbook pro (2.2 Ghz / 8GB ram / macosx 10.7.5) runs very often

Anybody any idea (preferably in german :-)

Greetings 

thomas