To add to the comments above; if you have a large user base & want to minimise disruption to services I suggest you run two BES in parallel whilst email accounts are gradually migrated from Domino to Exchange I suggest taking the following into consideration:


I would suggest you do the following: Purchase BlackBerry Enterprise Server for Microsoft Exchange.

Purchase some additional CAL's (e.g. minimum 20) to allow you to gradually delete user accounts off the BES for Domino & add to the BES for Exchange.
(You can copy the spare CAL's that become available as users are deleted from the BES for Domino & add the CAL's to the BES for Exchange).

Replicate the current BlackBerry Infrastructure & configure IT Policies etc for the new BES for Exchange.

Once a user account has been migrated from Domino to Exchange you can then delete the BlackBerry account on the BES for Domino & create a new BlackBerry account on the BES for Exchange. Note all user configuration (saved preferences) will be lost.

Wipe all data & applications off the users BlackBerry device, upgrade the BlackBerry device software if running an old version, perform a wireless enterprise activation of the BlackBerry device using the user account on the new BES for Microsoft Exchange.

As you can imagine this will be a time consuming task depending on how many BlackBerry user accounts you have. I would say that you could easily spend 2-3 hours per device if there are no errors during the process (that does not include setting up the account on the new BES for Exchange).

Refer to RIM KB 11141 ( BlackBerry Application Error