Errol Mangwiro wrote:
> Does anyone know of a way I can tighten fake sender policies & prevent
> this from occuring again?
Heinz Diehl wrote:
> You can't prevent people from faking the From: header.
But you can detect those fakes.
Bounces should be sent to the SMTP envelope FROM address, not the
address in the header. (For example, once this message has gone through
the fedoraproject.org servers, it will have an SMTP FROM address of
users-bounces@xxxxxxxxxxxxxxxxxxxxxxx , so mailman should get any
bounces, but it will still have
From: James Wilkinson <fedora@xxxxxxxxxxxxxxxxxx>
up there, so you lucky people can reply to me.
BATV is a technique for rewriting the SMTP FROM address to include a
cryptographic token that is unique to that email. Any bounces including
one of those tokens must at least have seen that email; any bounces to
the plain address must therefore have been sent in reply to something
that didn’t go through your servers.
BATV isn’t perfect, or at least, the rest of the Internet isn’t perfect.
It does things according to specs in ways some things don’t expect. It
also does require that all your outgoing email goes through
BATV-rewriting servers.
Alternatively, SpamAssassin has rules to detect bounces. A competent
mail filtering program should be able to filter all bounces into a
separate folder.
> Any spamfilter
> or network admin who tags email as spam according to From: is a moron.
Now that I would dispute: if the email purports to come from a known
spammer, then I don’t see why I shouldn’t gleefully reject or sort their
email accordingly!
You could compare it to an identity thief who stole the identity of
a known terrorist and flew into Washington, London or Jerusalem under
that identity.
Hope this helps,
James.
--
E-mail: james@ | [Alan] finally installed his cuckoo clock on the wall.
aprilcottage.co.uk | For some reason this involved falling over in the dark in
| the garden, but I haven't dared ask about that yet. I
| don't -think- he was trying to catch a cuckoo to put
| inside it, but you never know. -- Telsa Gwynne's Diary
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