Mail Server Relay Testing

As you may know, I am not big in the server world, even less into mail servers. They make me sick. But, today I found a nifty little tool you can use to test your mail server against many different types of relay attempts. Best of all, its dead simple. From your servers console, telnet to relay-test.mail-abuse.org. Here is the output from me testing the server I host my email and this site on.

tonhe@Benzaiten:~$ telnet relay-test.mail-abuse.org
Trying 168.61.4.13...
Connected to cygnus.mail-abuse.org.
Escape character is '^]'.
Connecting to 69.162.120.13 ...
<<< 220 Benzaiten.mattke.net ESMTP Postfix (Debian/GNU)
>>> HELO cygnus.mail-abuse.org
<<< 250 Benzaiten.mattke.net
:Relay test: #Quote test
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: <"nobody@mail-abuse.org">
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 1
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 2
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #test 3
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 4
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 5
>>> mail from: <>
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 6
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 7
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 8
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 9
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 10
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: <"nobody@mail-abuse.org">
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 11
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: <"nobody%mail-abuse.org">
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 12
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 501 5.1.3 Bad recipient address syntax
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 13
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: <"nobody@mail-abuse.org"@[69.162.120.13]>
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 14
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 15
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: <@benzaiten.mattke.net:nobody@mail-abuse.org>
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 16
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: <@[69.162.120.13]:nobody@mail-abuse.org>
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #Test 17
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #test 18
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 250 2.0.0 Ok
:Relay test: #test 19
>>> mail from: 
<<< 250 2.1.0 Ok
>>> rcpt to: 
<<< 554 5.7.1 : Relay access denied
>>> rset
<<< 421 4.7.0 Benzaiten.mattke.net Error: too many errors
Connecting to 69.162.120.13 ...
<<< 220 Benzaiten.mattke.net ESMTP Postfix (Debian/GNU)
>>> HELO cygnus.mail-abuse.org
<<< 250 Benzaiten.mattke.net
>>> QUIT
<<< 221 2.0.0 Bye
Tested host banner: 220 Benzaiten.mattke.net ESMTP Postfix (Debian/GNU)
System appeared to reject relay attempts
Connection closed by foreign host.

Tony Mattke

Network engineer turned management currently servicing the enterprise data center market. I started working on networks in the ’90s and still feel like that was just a few years ago. Jack of all trades, master of none; I love to learn about everything. Feel free to ask me about photography, woodworking, nhra, watches, or even networking! — For feedback, please leave a comment on the article in question, and I’ll respond as soon as I can. For everything else including fan mail or death threats, contact me via twitter.