Blackberry 7100 and Exchange Server Mapi clients

[Jimbo]

My two bosses, who have been using Blackberrys for years, recently
upgraded to 7100's.

Our corporate network supports Exchange 2003 for email.

When they are logged onto Exchange as a MAPI client, they do not get
their emails sent to their blackberries. If they log off, they do.

(This is NOT what happenned previously)

When we called AT&T, they said there is something we have to do with
the Server, but they didn't know what it was.

None of my Exchange gurus are aware of anything like this - can someone
shed some light on this ?

Many Thanks

JM