has developed the following free services to help in this effort. Senders, ISP's and other third party senders and service providers should actively manage the reputation of your outbound IPs. While, other forms of authentication are available, Microsoft currently only validates inbound mail via SPF and Sender ID authentication. This is the practice of verifying email addresses without sending (or attempting to send) emails to those addresses.Įmail sent to users should include Sender ID authentication. Senders must not use namespace mining techniques against inbound email servers.Email servers must have valid reverse DNS records.Connections from dynamic IP space may not be accepted.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.Messages must not be transmitted through insecure email relay or proxy servers.Sender must not open more than 500 simultaneous connections to inbound email servers without making prior arrangements.After multiple non-delivery responses (see #2), the sender must cease further attempts to send email to that recipient.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.Sender is expected to comply with all technical standards for the transmission of Internet email, as published by The Internet Society's Internet Engineering Task Force (IETF), including RFC 2821, RFC 2822, and others.In addition, email servers connecting to must adhere to the following requirements:

Microsoft to do best practices