glimbeek - 7:08 am on Feb 9, 2010 (gmt 0)

Not sure I'm getting you kaled, but I used your example:

username1@example.com and username@example1.com ofcourse with the email address that's not working not with example1.com :P

And the username1@example.com fails with the "550 "Unknown User"" error and the username@example1.com fails with a "Mail delivery failed: returning message to sender".

Not sure what this means though...