Open Mail Relay

Jon Radel jon at
Sat Aug 14 19:54:21 UTC 2010

On 8/14/10 11:05 AM, Mikhail wrote:
> On 14.08.2010 17:29, peter at wrote:
>> I've reviewed my mail logs for the past couple of days and I can't
>> find any entries for any mail addressed to the complainer's domain
>> name except mail that should have been sent.
> You can try it yourself, with telnet and proper smtp commands. For
> example, telnet from outside of your organization to your mail server
> and issue:
> ehlo
> mail from: foobar at
> rcpt to: foobar at
> data
> test mail
> .
> You actually have to get error message about relay denied for you. If
> you don't - you're in trouble.
> If you do recieve such message - you relay is closed and probably you
> have spam worms who send emails from legit user, or something like that.

The basic test, but hardly sufficient to determine if all the known ways 
of fooling an smtp server are accounted for.  Recall from the OP's 
description: "saying relaying was denied in 17 separate tests."

The above also can be an issue if you do the test from an IP address 
that the SMTP server has been configured to treat as "trusted."

--Jon Radel
jon at

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