Re: People forging their From: addresses

[Freek de Kruijf <]

Nate Waddoups wrote:
> ...
> I cannot help but wonder why spammers choose to use legitimate domain
> names when they forge "From" headers.  What good could it possibly do
> them, as opposed to just using something that doesn't exist?
> Puzzling.

A lot of e-mail systems check the from-address for existance. If this
address does not exist the message is not accepted.

Unfortunately a lot of these e-mail systems use the wrong return code.
When the domain does not exist they should permanently reject the
message; in SMTP-terms an 500 error code should be given, however often
a 400 error code is given. This 400 error code should only be given in
case the DNS system is not responding on the request.

fr.gr.

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