At my institution just moved from a on-premise e-mail solution to a hosted e-mail solution. Once we moved the MX record for e-mail servers, when some of our BIS customers reconfigured their BIS settings for the new e-mail server, BIS would change the settings back to the non-existent previous mail server domain name. This occured whether they made the configuration changes on the device or via the BIS website. The cellular provider is saying it is a RIM problem.
However, we have only had a handful of calls, but we cannot find a rhyme or reason for this to occur.