One of our clients has suddenly found a new problem - his mails are rejected by Hotmail with this error message:
I have taken up this issue with MSN Postmaster through this page: MSN PostmasterRemote host said: 550 DY-001 Mail rejected by Windows Live Hotmail for policy reasons. We generally do not accept email from dynamic IP's as they are not typically used to deliver unauthenticated SMTP e-mail to an Internet mail server. The Spamhaus Project maintains lists of dynamic and residential IP addresses. If you are not an email/network admin please contact your E-mail/Internet Service Provider for help.
I checked out that the domain is not black listed. And after a detailed analysis, it is found that Gmail also drops the mails quietly without rejecting them. But mails emanating from the client's mail server reaches other domains with out any melodrama.
What do I miss here ?