E-mail sent to the MSN Hotmail and Windows Live Services should comply with the documents listed below (some links are only available in English)
Anti-spam Recommendations for SMTP MTAs (BCP 30), The Internet Society
SMTP Service Extension for Command Pipelining (STD 60), The Internet Society
“Remove Me” Responses and Responsibilities: E-mail Marketers Must Honor “Unsubscribe” Claims, Federal Trade Commission
Basic Mailing List Management Guidelines for Preventing Abuse, Mail Abuse Prevention System
Make sure your content complies with the following guidelines:
Sender is expected to comply with all technical standards for the transmission of Internet e-mail, as published by The Internet Society’s Internet Engineering Task Force (IETF), including RFC 2821, RFC 2822, and others.
After given a numeric SMTP error response code between 500 and 599 (also known as a “permanent non-delivery response”), the sender must not attempt to retransmit that message to that recipient.
After multiple non-delivery responses (see #2), the sender must cease further attempts to send e-mail to that recipient.
Sender must not open more than 500 simultaneous connections to MSN Services inbound mail servers without making prior arrangements.
Messages must not be transmitted through insecure e-mail relay or proxy servers.
The mechanism for unsubscribing, either from individual lists or all lists hosted by the sender, must be clearly documented and easy for recipients to find and use.
Connections from dynamic IP space may not be accepted.
Email servers must have valid reverse DNS records.