Any changes to client desktop configuration or network? For example, SP2
for Windows XP was released a while back and folks are just starting to
deploy in corporate environments. Considering that SP2 for Windows XP
automatically turns on the built-in firewall and the firewall is known to
block the incoming UDP packet, this would trigger Outlook 2003 to fall back
to polling. If this sounds like a candidate, then
http://support.microsoft.com/default.aspx?scid=kb;en-us;264035 might be what
you need to tell Outlook 2003 to use a fixed udp port. From there an active
directory gpo could configure the firewall to allow comms on said port.
As for activity, I'm not sure what your environment is like so I can't
answer. I just think it is silly to have Outlook poll the server once every
minute considering that the average user doesn't see 1 message every minute.
If I received one message every minute, I'm guessing something is seriously
wrong.