In my zimbra mail each time I send any mail to Hotmail or Gmail I keep getting the following failure message delivery as an example:

<waseem_p17@hotmail.com>: host mx4.hotmail.com[] 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. Email/network admins, please
visit MSN Postmaster for email delivery information and support
(in reply to MAIL FROM command)

So, How I can solve this problem.