ISPs are clamping down on port 25, preventing users from using 3rd-party SMTP servers such as Birdhouse’s, even with authentication. Some have even gone as far as requiring outbound mail to belong to a domain the ISP knows it controls. All a well-intentioned — but naive — attempt to thwart spammers.
Unfortunately, the trend makes it difficult for Birdhouse to offer SMTP services to a lot of customers. At this point, I simply recommend up front that people use their ISP’s SMTP for outgoing mail.
Now add to this the hassle of using a laptop and traveling from place to place — I hear from some customers who are changing their SMTP servers several times a day. And I hate recommending webmail because I myself hate webmail with a passion.
Solution: Birdhouse needs to open an alternate SMTP port, which people could use from anywhere. cPanel makes this easy to do, but the question is, which port to use for the SMTP alternate? In the first few hours of experimentation, have already discovered that SBC/Yahoo! also blocks port 26, which is the cPanel recommendation. In fact, some ISPs may be preventing their customers from using all non-standard ports.
mneptok helped to clarify the question: Need to choose a port that’s common enough to not be considered non-standard, but that we also don’t need for anything else. If you’re using one of the big commercial providers for connectivity and have found surprising ports blocked, let me know!
I remember in the early-mid-90s, it was still possible to find wide-open public mail relays, and it wasn’t even considered a problem. Now it’s hard even to use closed private relays. Doing business in a world full of bad guys is a drag.
Music:
T.Rex :: Chariots of Silk
Got partway through Jim Jarmusch’s 
