Open Mail Relay

Erik Norgaard norgaard at
Sun Aug 15 20:16:01 UTC 2010

On 15/08/10 13.57, peter at wrote:

> Assume, as Mr. Bonomi suggests, that some bad guy has installed some type of additional mailer on the machine or another machine that's allowed to relay mail.  How would I go about locating that other mailer?

If the messages are indeed relayed through your server then you can see 
it in the logs and in the Received header field which host is sending 
the mail to your server.

If somebody forges mail to appear to come from your domain, but not 
relayed through your server there is really not much you can do. Only 
the recipient server can reject the mails.

Some servers support spf and you can help other servers know that mail 
from your domain must originate from your server by adding a txt entry 
in your dns.

BR, Erik

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