I´m use Centos 4 with ISPConfig, all work perfect, except when i send mail to hotmail or yahoo. Always return this messagge: This is the Postfix program at host localhost.localdomain. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to <postmaster> If you do so, please include this problem report. You can delete your own text from the attached returned message. The Postfix program <firstname.lastname@example.org>: host mx4.hotmail.com[18.104.22.168] said: 550 Your e-mail was rejected for policy reasons on this gateway. Reasons for rejection may be related to content such as obscene language, graphics, or spam-like characteristics (or) other reputation problems. For sender troubleshooting information, please go to http://postmaster.msn.com. Please note: if you are an end-user please contact your E-mail/Internet Service Provider for assistance. (in reply to MAIL FROM command) ------------------------- But if i send another domain work perfect, some can help me????, thanks a lot.