Mailing lists are a great resource, even in this Latter-Day Dispensation of Search Engines and Web Forums. While web forums have their place, there's nothing like being able to carry on an extended conversation in the comfort of your own Inbox. I was inspired by a drive-by comment on a recent thread I participated in to take a step back and examine the practice of port-blocking TCP 25, which is the port used by the Simple Mail Transfer Protocol (SMTP).