On Tue, 26 Jun 2007 16:25:53 -0400, John Cunniff <[log in to unmask]> wrote: >5.1.1 550 In addition to what the others have said, these error codes mean 5.1.1 Bad destination mailbox address The mailbox specified in the address does not exist. (RFC 1893) 550 No such user here (RFC 821, RFC 2821) All error codes beginning with 5.x.x or 5xx are permanent errors. Trying again will not result in success. So I would immediately delete the address without further ado.