In the last 12 hours several of my Gmail accounts have had email bounced back from HOTMAIL. It could be related to the IP address of my ISP (Verizon FIOS), but it seems odd.
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