OpenBSD-current now has 'smtpctl spf walk'
by from OpenBSD Journal on (#3CSDX)
If you run a mail service, you probably like to have greylisting in place, via spamd(8) or similar means. However, there are some sites that simply do not play well with greylisting, and for those it's useful to extract SPF information to identify their valid outgoing SMTP hosts.
Now OpenBSD offers a straightforward mechanism to do that and fill your nospamd table, right from the smtpctl utility via the subcommand spf walk. Gilles Chehade (gilles@) describes how in a recent blog post titled spfwalk.
This feature is still in need of testing, so please grab a snapshot and test!