I'm getting the next error from my postfix server: Jun 21 11:01:23 subinasmail postfix/smtp[26564]: 5D60D28ACA7: to=<irontec23@hotmail.com>, relay=mx3.hotmail.com[65.55.92.136]:25, delay=1.2, delays=0.04/0.05/0.86/0.24, dsn=5.0.0, status=bounced (host mx3.hotmail.com[65.55.92.136] said: 550 SC-001 (SNT0-MC1-F47) Unfortunately, messages from 77.229.182.21 weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. (in reply to MAIL FROM command)) And after that I get a mail to the account which is sending mail. My server correo.subinasyurrutia.com which IP is 77.229.182.21 This message appears sending any mail from any account @subinasyurrutia.com (it has about 15 accounts) to any hotmail account. I have checked the IP in http://whatismyipaddress.com/blacklist-check and it doesn't appear in any blacklist. I have complete the form in https://support.msn.com/eform.aspx?productKey=edfsmsbl&ct=eformts&st=1&wfxredirect=1&wa=wsignin1.0 2 weeks ago but I still having the problem. Any solution to this? I'm not having any problem with other domains. Thanks