Exchange 2003 environment Mail is working fine 99.9% of the time, e-mail out, e-mail in, no issues. Then every once in a while lately I will see users that get messages from the System Adminitrator account that say, "Your message did not reach some or all of the intended recipients. The following recipient(s) cannot be reached: firstname.lastname@example.org on ... You do not have permission to send to this recipient. For assistance, contact... This only happens here and there, so it isn't like a permission is there one minute and then gone the next. Any ideas on where to start looking for a problem that only happens here and there?
Software/Hardware used: Exchange 2003 on Dell PowerEdge