I have an email server which hosts 3 domains. I have reason to believe that microsoft maintains an outgoing blacklist and would like confirmation on this. I have had many a report that people on domains hosted on hotmail/outlook are getting messages bounced back stating that our server was unreachable. This only happens for one of the three domains hosted on our server. I went to outlook.com and setup an account. When I create a new message and enter the recipient at that affected domain, the address immediately turns red, and when I hover over it states that the address may not be valid. This happens without ever sending a packet to our servers. The affected domain can send emails to hotmail/outlook accounts just fine. Anybody have some recommendations on how I resolve this, as Microsoft support seems to be under technical. Thanks, Todd K. Grand