Some of you may have experienced a problem with Warhorn mysteriously refusing to send you email. I identified a while back that this was happening with some Hotmail users, but I was never able to track down the problem.

After moving to the new server, some new troubleshooting capabilities helped me determine the issue was with Hotmail’s implementation of SPF, or Sender Policy Framework, a relatively new email standard that helps combat email forgery.

Here’s what was happening: Warhorn would send an email message using the address of the event organizer (e.g. somebody@hotmail.com), and Hotmail would refuse to deliver the message because the Warhorn server was not authorized to send messages from hotmail.com. Bad news.

I have updated Warhorn to now send all email from a warhorn.net address. This should resolve the problem of mysteriously missing messages. If anybody continues to see a problem with dropped email, please let us know (though, as always, make sure your spam filters are letting warhorn.net through). Thanks!