Okay, odd… I’ve just realized I’ve been on the SquirrelMail project now since about 2002, and in the 4 years I’ve been on the project, I don’t believe I’ve written a single plugin. Most unusual, however today I remedied that with a request in #squirrelmail for a new version of ip_user. I quickly knocked together ip_restrict which basically restricts users to certain IP addresses, or networks, depending on your configurations. You can download it here.