This days I have a problem with delivey mails to hotmail.com.
I have a custom mail server with few domains.
Error they receive:
Jul 4 10:57:04 server postfix/smtp[33544]: E4904238083C: to=userxdret-hiddenzzzz@hotmail.com, relay=mx1.hotmail.com[104.44.194.237]:25, delay=1.7, delays=0.08/0.01/1.5/0.16, dsn=5.0.0, status=bounced (host mx1.hotmail.com[104.44.194.237] said: 550 SC-001 (SNT004-MC11F10) Unfortunately, messages from 86.126.138.62 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))
Jul 3 10:57:04 server postfix/smtp[33544]: E4904238083C: lost connection with mx1.hotmail.com[104.44.194.237] while sending RCPT TO
I have already setup SPF, DKIM and DMARC on my server and DNS.
Solutions: Go to this link: https://support.live.com/eform.aspx?productKey=edfsmsbl3&ct=eformts&wa=wsignin1.0&scrx=1 and submit your problem delivery mail to hotmail.com, outlook.com, live.com or other domain hosted on this email platform.
You will receive an automated email in few hours with answer.
INFO: If you have other problem with spam or other email account on your server is used for spam you have to solve this problem first.
Link with few website to check blacklist:
https://mxtoolbox.com/blacklists.aspx
http://blacklistscan.com/
https://www.senderscore.org/
Have a great day !