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Old 05-07-2005, 12:45 AM   #1
jamesdin
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Open relay SMTP


I've scanned my mail server and got a warning about open SMTP relay. I'm a little confused because I read emails only trough imap. This is the list of open ports:

22/tcp open ssh
25/tcp open smtp
80/tcp open http
143/tcp open imap
220/tcp open imap3

Yes, smtp is open, but if I try to send an email trough my mail server (eg mail.tld.com) with an email address that has a different domain (eg me@different.domain.com) I get an error -- no mail is relayed.

Am I missing something?
How do I find out what SMTP daemon is used?
 
Old 05-07-2005, 01:07 AM   #2
Matir
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Your system seems to be correctly configured: it should not relay mail for other domains. I'm not exactly sure which test was returning these results, telling you you had an open relay.
 
Old 05-07-2005, 02:08 PM   #3
jamesdin
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After using some more reliable open relay tests it truns out that my SMTP is not really open; it authenticates users by domain name. I was told this could be easily spoofed but... I'm not sure how to enalbe SMPT authentication. I'm using exim and postfix. Any suggestions or pointers?

I'm not sure if its exim or postfix that's SMTP. Is there a way to find out?
 
Old 05-07-2005, 04:06 PM   #4
DaWallace
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both of them.. along with about 5 others.
 
Old 05-07-2005, 04:34 PM   #5
jamesdin
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Huh?

BTW I found out that SMTP is postfix.
 
Old 05-09-2005, 05:11 PM   #6
jeru
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to find out what it is usually all you have to do is;
telnet mail.domain.com 25

for instance if I do it to mine I would see
220 mail.domain.com ESMTP Postfix (Debian/GNU)

But that isn't always true, just most people have the banner turned on that way. Also, if you want a pretty good relay test for open relays. From the system you want to check do a;

telnet relay-test.mail-abuse.org

the remote system will run a series of checks against the machine your are telneting from, and tell you if it can get around your configuration.
 
Old 05-20-2005, 10:27 AM   #7
kevin.kevinh
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When I tried 'telnet relay-test mail-abuse.org', I got:

Trying 168.61.4.13...
Connected to relay-test.mail-abuse.org.
Escape character is '^]'.
/proj/maps/bin/in.relaytest: socket failed [Bad file descriptor]
Connecting to xxx.xxx.xxx.xxx ...
Connection closed by foreign host.

(I've obscured my IP address here with xxx.xxx....)

What does this indicate?
 
  


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