MailServer

Postfix Tutorials

• RedHat: https://www.redhat.com/sysadmin/install-configure-postfix
• Linux.com: https://www.linux.com/training-tutorials/install-and-configure-postfix-mail-server/
• Postfix: http://www.postfix.org/BASIC_CONFIGURATION_README.html
• DigitalOcean: https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-on-ubuntu-20-04
  • Interesting - see: sudo DEBIAN_PRIORITY=low apt install postfix

SPF DNS Entry

Traxel Settings

• IPV4: 69.10.40.10
• IPV6: fe80::d227:88ff:fe34:7999/64
• Format: v=spf1 ip4:40.113.200.201 ip6:2001:db8:85a3:8d3:1319:8a2e:370:7348 include:thirdpartydomain.com ~all

• Start with the SPF version, v=spf1.
  • Indicates that this is an SPF record.
  • Will always be spf1 as other SPF versions have been discontinued.
    • We'll only ever need 640K of RAM.
• Next, all IP addresses that are eligible to send email on behalf of your domain.
  • Space delimited
  • prefix ip[n]:
  • ip4:69.10.40.10 ip6:fe80::d227:88ff:fe34:7999
• Next comes the include statement, which lists every third party organization that sends email on your behalf.
  • Does this mean interserver? Is this the part where reverse lookups come in?
  • include:thirdpartydomain.com
• The end of the SPF record is the strictness level.
  • "-all" - strictest, fail email that doesn't come from this ip list
  • "~all" - accept but flag email from other servers
  • "+all" - anything goes
  • I'll be using "-all".

Looks like the only remaining question is the "include" tag. How do I handle the include tag and/or flag my server from the reverse lookup standpoint?

• If no include:
  • v=spf1 ip4:69.10.40.10 ip6:fe80::d227:88ff:fe34:7999 -all
  • This works. Problem solved. Grumble.
• If yes include:
  • v=spf1 ip4:69.10.40.10 ip6:fe80::d227:88ff:fe34:7999 include:systemicbias.com -all