I have a send-only mail server setup on an Ubuntu VPS. The mail server is only used to send out registration e-mails from a web application. I have the following configured:
- DomainKeys Identified Mail (DKIM)
- Sender Policy Framework (SPF)
- DMARC
- Resolvable hostname
- rDNS
I've also tested my mail server with mail-tester.com and gotten a 10/10 rating (See report). The following is from my mail.log:
Mar 13 14:44:16 server postfix/pickup[5922]: 8147712289A: uid=33 from=<noreply@my-domain.me>
Mar 13 14:44:16 server postfix/cleanup[6311]: 8147712289A: message-id=<43fd440eaa77a6bb9f4b28e608f4c335@bugs.my-domain.me>
Mar 13 14:44:16 server opendkim[943]: 8147712289A: DKIM-Signature field added (s=mail, d=connect-ats.com) Mar 13 14:44:16 server postfix/qmgr[1102]: 8147712289A: from=<noreply@my-domain.me>, size=982, nrcpt=1 (queue active)
Mar 13 14:44:16 server postfix/smtp[6313]: 8147712289A: to=<ralph@outlook.com>, relay=mx2.hotmail.com[65.54.188.72]:25, delay=0.38, delays=0.07/0.01/0.23/0.07, dsn=5.0.0, status=bounced (host mx2.hotmail.com[65.54.188.72] said: 550 SC-001 (BAY004-MC1F33) Unfortunately, messages from 159.203.23.75 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))
Mar 13 14:44:16 server postfix/smtp[6313]: 8147712289A: lost connection with mx2.hotmail.com[65.54.188.72] while sending RCPT TO
Mar 13 14:44:16 server postfix/cleanup[6311]: DD9C612350D: message-id=<20160313134416.DD9C612350D@server.my-domain.me>
Mar 13 14:44:16 server postfix/qmgr[1102]: DD9C612350D: from=<>, size=3860, nrcpt=1 (queue active)
Mar 13 14:44:16 server postfix/bounce[6314]: 8147712289A: sender non-delivery notification: DD9C612350D Mar 13 14:44:16 server postfix/qmgr[1102]: 8147712289A: removed
Mar 13 14:44:17 server postfix/smtp[6313]: DD9C612350D: to=<noreply@connect-ats.com>, relay=none, delay=0.21, delays=0/0/0.21/0, dsn=5.4.6, status=bounced (mail for my-domain.me loops back to myself) Mar 13 14:44:17 server postfix/qmgr[1102]: DD9C612350D: removed
I have gone over my configuration multiple times and the only thing I've found that may be an issue is the message ID, included in the log above. The web app is running at bugs.my-domain.me while I'm sending e-mails as noreply@my-domain.me and I don't have SPF settings for that domain,