Audience
For shops that have Lotus Domino version 8.0 or later for their mail and BES servers. This is a known issue listed in the release note for BES 5.0 Domino. (Source: http://na.blackberry.com/eng/deliver...ease_notes.pdf , page 17)

SDR 287348
In a Lotus Domino version 8.0 environment, the BlackBerry Messaging Agent might take longer than expected to send messages and calendar items to BlackBerry devices, and in certain circumstances, BlackBerry devices might not activate with the BlackBerry Enterprise Server. This issue impacts users whose mail file path in the operating system has a different case than the mail file path specified in the person document.

Workaround
Perform one of the following workarounds:
(1) Verify that the mail file path for users in the operating system is the same as the mail file path for those users specified in the person document.
(2) In HKEY_LOCAL_MACHINE\SOFTWARE\Research In Motion\BlackBerry Enterprise Server\Agents, change the DWORD value PollByMailServer to 0.