I'm honestly trying to figure out whether any mail systems treat mail
from sub.foo.com as being from foo.com when they make decisions about
sorting, filtering, and so forth.
SpamAssassin does this to a degree. It itself white-lists and in it's
documentation encourages others to white-list using
*(_at_)*(_dot_)foo(_dot_)com(_dot_) Even
though other measures might verify that the message isn't a forgery,
these white-listed entries still treat all sub-domains equally (by
imputing trust and foregoing filtering entirely).
SpamAssassin's actual tests performed on From: values treat all
sub-domains equally at least when the tests are performed upon the
local-part. This might be expected but it is an example of a mail
filter system treating *(_at_)*(_dot_)foo(_dot_)com identically.
Arvel
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