Penguins-On-Hudson

Shortly after I last upgraded my mail server, one user reported that his mail client was failing to connect with the message:

"Unable to connect to your IMAP server. You may have exceeded the maximum number of connections to this server..."

He was the only one known to be having this issue, so after a cursory check of the server with no obvious problems, I suggested that this might be an error on his end, such as connecting to the secure IMAP port without using SSL/TLS. Occam’s Razor suggests that a server error is more likely than a client error which just happens to coincide with a server upgrade, so I eventually decided to dig up some infrequently used commands and perform a thorough analysis. (more…)

Some time ago I enabled recipient delimiters (e.g. user+foo@host.tld) as a convenient way to know if shady web forms are contributing to my spam folder. The idea is that when House Depot requires me to have an account before I can see if they have loose screws in stock locally, I can sign up with garrison+housedepot@codefix.net instead of my usual e-mail. With recipient delimiters enabled, postfix will try to deliver any incoming mail to garrison+housedepot but when it finds no such user, it will try garrison and I get my mail. The problem arises when I discover that House Depot’s broken web form rejects any e-mail addresses with “+” in the user name as invalid. I’m already using garrison+foo style addresses elsewhere so I don’t want to change the recipient delimiter, but neither do I trust my real address to a company that can’t even create a proper web form. (more…)