[Dshield] smtp test for open relay

Fred Grayson fred at fred-grayson.net
Mon Jun 23 14:35:11 GMT 2003

Uhm, no, sorry Joe's advice was not correct with respect to my post. Here's why:

Marc Chabot, the original poster has a mail server he wants tested to determine if it is an open relay. 
My suggestion was for him to access that machine and:

telnet relay-test.mail-abuse.org

The result of this is that the machine at mail-abuse.org will back connect to Marc's mail server and 
attempt to relay mail thru it with a rather extensive set of relay tests, most of which are nontrivial 
compared to what most folks suggest trying by hand via a normal smtp session.

Joe's suggestion "Try telnet relay-test.mail-abuse.org 25......" does absolutely nothing for Marc or 
anyone else with respect to testing their own mail servers.

Of course, if you do have your own mail server, you could always wander over to the console, or telnet 
or ssh into it, do as I suggested and see that what happens is exactly what Marc was looking for.

I hope this clears it up for everyone.

>Uhm . . . No, sorry.  His advice was sound.  Another way is to use
>Netcat, but telnet <host> 25 works just fine if you want to connect to
>> -----Original Message-----
>> From: Fred Grayson [mailto:fred at fred-grayson.net] 
>> Sent: Monday, June 23, 2003 7:02 AM
>> To: list at dshield.org
>> Subject: [Dshield] smtp test for open relay
>> Incorrect advice Joe. Connecting to the telnet port is the 
>> way it works.
>> >Try telnet relay-test.mail-abuse.org 25
>> >
>> >Without the 25 you'll be attempting a telnet session and
>> >not a SMTP session.
>> >After connecting, you'll need to spoof an SMTP transaction using the 
>> >traditional helo, mail from: , and rcpt to: followed by data 
>> then the 
>> >content.
>> >
>> >cheers
>> >-Joe
>> >
>> >-----Original Message-----
>> >From: Fred Grayson [mailto:fred at fred-grayson.net]
>> >Sent: Monday, June 23, 2003 9:12 AM
>> >To: list at dshield.org
>> >Subject: [Dshield] smtp test for open relay
>> >
>> >
>> >>Hi.
>> >>
>> >>Do you have links to ips web sites (or others) that test for open 
>> >>relays for an IP ?  I've got one to test and I don't know 
>> where to go.
>> >
>> >If you have access to the machine running the mail server 
>> itself, you 
>> >can test it. Just run this from a shell:
>> >
>> >telnet relay-test.mail-abuse.org
>> >
>> >
>> >

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