Looks like Hotmail may be having sporadic issues sending email. Occasionally, Hotmail users sending messages to our domain get a “Delivery Status Notification (Failure)” with the following details:

Final-Recipient: rfc822;xxx@stmarkdc.org
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;550-bay0-omc2-s25.bay0.hotmail.com [65.54.246.161]:57850 is currently not
550-permitted to relay through this server. Perhaps you have not logged into
550-the pop/imap server in the last 30 minutes or do not have SMTP
550 Authentication turned on in your email client.

I have checked with the users and they are using the normal Hotmail web client. Also, on #citrt irc channel, another church was having the same issue. We use Katharion for message filtering and they use Postini, so it’s probably not an issue with filtering. The server listed for their failure was bay0-omc3-s28.bay0.hotmail.com, which is on the same class C subnet. Please comment below if you are having similar issues.