One of the execs at work suddenly stopped receiving emails on his blackberry today. After some testing it was determined that his blackberry account was being returned with a 550 Address Rejected error. Thanks to this blog entry I was able to get him going again.
Basically what has happened, if you don’t feel like following the above link, is that AT&T has stopped forwarding mail to mycingular.blackberry.net. All you need to do to correct this is replace mycingular with att. Like so, email@example.com instead of firstname.lastname@example.org. Ta-da, email is working again. Thank you Ken Hanscom for blogging about this, as I’m not a blackberry user and never got the email explaining the cut off date for the mycingular server.