How can I prevent Exchange from continually disconnecting users?

I am having issues where my users keeps disconnecting from the exchange server. I dont know why it keeps doing it but I did try my best to figure out the issues. The exchange server is just eating lots of bandwidth and I dont experience this before it just started after I setup the sonicwall and branch network setup. I use windows server 2008 and exchange 2007.
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make sure port 25 & 110 are open on your firewalls...

try to change your exchange account settings in outlook to cached mode.

also, are you running wins?  if you are, do you really have to?

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bobox00Author Commented:
The firewall was blocking packets.
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