Are there any circumstances that a mail server should ever send to the A record of a domain when that domain has MX records pointing elsewhere?  We recently had a network outage so all mail servers were down. So if  Stanford couldn't get to the machines pointed to by the MX records, can it grab the A record as a legitimate destination for email (and cache that result).  I've turned off the mail server functionality of the webserver in the short term but I can't understand why I need to?