Mail flow › Receiving › Sender checks opens with one choice instead of
six strategy fields, and a table of what each level does to mail that
fails. From the SMTP code:
- Relaxed (the stock settings): SPF, DKIM, DMARC and reverse DNS are
checked on port 25 and scored by the spam filter; nothing is refused.
- Recommended: also refuses mail that fails DMARC for a domain that
publishes p=reject, and checks ARC.
- Strict: also refuses senders that fail reverse DNS or SPF on MAIL
FROM (including senders with none), and broken ARC chains. It warns
that some real mail from small or badly set-up servers will bounce.
No level refuses unsigned mail (strict DKIM, which RFC 6376 advises
against). Checks stay on port 25, like the stock settings. Values set by
hand show as "Set by hand below", and applying a level then says it
replaces them. The form reloads after a level is applied; DKIM signing
isn't touched.
jcoffey-dev