I have done this in the past for certain situations but I did have this working on the old version of mercury, when I upgraded to the latest version is when I started having the issue

Having issue with blackberry running imap to pull email to blackberry device.  It seems to work ok when not logged into pegasus client locally, but when pegasus is open I can see the connection comming in to the imap module and then just stays connected never dropping tht econnection

I have found it best to simply forward any incoming emails directly to the blackberry device.  I have a forwarding rule for the local user in mercury to the blackberry address.
 

Jim