SPF

Sites

• http://www.open-spf.org/
• https://mxtoolbox.com/SPFRecordGenerator.aspx
• https://www.spfwizard.net/

Docs

• https://dmarcian.com/spf-syntax-table/
• Setting Up SPF, SenderId, Domain Keys, and DKIM
• http://en.wikipedia.org/wiki/Sender_Policy_Framework
• http://homepages.tesco.net/J.deBoynePollard/FGA/smtp-spf-is-harmful.html
• SPF overview
• Why not spf

Tools

• pyspf
• Validate SPF record

FAQ

softfail ~all

A soft fail means that emails from unauthorized senders are not discarded but forwarded to a spam folder, or marked suspicious.

== hardfail -all ==

All other senders—those not listed in the record—are unauthorized, and their emails are discarded.

+all, -all, ~all?

+all

Any server can send

Check SPF record of a host or domain

dig domain.com TXT

or

dig host.domain.com TXT

SPF - Returned fail

Misconfigured SPF record or spoofed "From" address