Willem Kossen wrote:
pobox.com text "v=spf1 mx mx:fallback-relay.%{d} a:smtp.%{d}
a:emerald.%{d} redirect=%{l1r+}._at_.%{o}._spf.%{d}"
[...]
the %{l1r+} part that somehow has to do with the
username-part of the emailaddress escapes me completely
Whatever it is, it's fascinating... ;-) Here's my 1st guess:
It's a sender policy for pobox.com, therefore it's applied on
something like MAIL FROM:<user(_at_)pobox(_dot_)com>
The simple cases are IPs matching the MX of pobox.com, or the
MX of fallback-relay.pobox.com, or the IPs of smtp.pobox.com
resp. emerald.pobox.com
Obviously not good enough for some users (local parts, macro
"l"). The "l1" means "take one part of the local part," the
"l1r" means "take one part of the reverse local part", and
"l1r+" means "one part of the reverse local part split at +".
Putting it all together some+weird+address(_at_)pobox(_dot_)com should
result in address._at_.pobox.com._spf.pobox.com (?) But now
I'm lost with the difference between %{o] and %{d}, see also
<http://article.gmane.org/gmane.mail.spam.spf.discuss:6507>
i don't understand what the redirect statement tries to
accomplish here.
It's a per user policy, somebody using
(_dot_)(_dot_)(_dot_)+address(_at_)pobox(_dot_)com
sends his mail not only via the normal pobox.com mailers, but
also via mailers found in the sender policy for the (dummy)
domain address._at_.pobox.com._spf.pobox.com (?)
You find it in chapter 7 (macros) of the original SPF draft
<http://spf.pobox.com/spf-draft-200406.txt> resp. on the page
<http://spf.pobox.com/macros.html>
Bye, Frank