Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 12): 550 SC-001 Mail rejected by Windows Live Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation problems. If you are not an email/network admin please contact your E-mail/Internet Service Provider for help. Email/network admins, please visit http://postmaster.live.com for email delivery information and support
I'm using Google Apps, and both the outgoing and incoming mails to/from Hotmail seem to fail.
Regarding the IP-addresses, I wouldn't have a clue due to Google's environment.
@bithost(NET) Umm "yeah", but it's not me using Hotmail though.
Anywho, this is basically a first for me regarding bot in and outing mail to/from Hotmail being blocked. I've seen emails disappearing in thin air while sent from Hotmail though, but not at the same time.