Sendmail Header Checking - From:

[Le Gazman]

Hi there,

To protect against spoofing I've setup separate incoming and outgoing SMTP servers. On the incoming side I've blocked our own domains using the access_db, since we will never send through them. This has stopped a lot of emails from senders pretending to be from our organisation, so it was a partial success.

However, this only blocks envelope MAIL FROM, so people have now cottoned on to this and have started spoofing the From: header instead.

I'm aware there are now header checks in sendmail, but I've got no idea how to set up my sendmail.mc to use them. Does anyone have some sample files they could show me? Basically I just want to add our own domains to it, the same way I did in the access_db.

Thanks,

[Claus Aßmann]

Le Gazman wrote:

> I'm aware there are now header checks in sendmail, but I've got no idea how to set up my sendmail.mc to use
> them. Does anyone have some sample files they could show me? Basically I just want to add our own domains to
> it, the same way I did in the access_db.

You could start by looking at
http://www.sendmail.org/~ca/email/chk-810n.html
It might give you some ideas -- but you have to "customize"
the rules for your own purpose(s).


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