Below is my configuration. When my users send to external e-mail addresses (internet e-mail), they are reporting that the client will lock up for a few seconds to maybe 30 seconds if lots of external users. I did not have this problem with GroupWise 7. I want to say it is happening since we went to GroupWise 8 MTA/POA (backend) and not the upgrading the client from 7 to 8.

Windows XP w/SP3
GroupWise 7.0.3 HP4 or 8.0.1 HP1

Server (I have 8 Postoffices each on it's own server, 3 have Domains on them)
Windows 2003 R2 w/SP2
GroupWise 8.0.1 HP1