Topic: NEED TO BLOCK SMTP OPEN RELAY TO AVOID SPAM

[microlatina]

Hi friends. I am a newbie to SME. I am in trouble because my ISP is telling me that he can perfectly Telnet my SME on port 25 SMTP. I did some research and found the following:

"One file controls access to the SMTP server.  It is /etc/smtpd_check_rules which is actually a link to /var/spool/smtpd/etc/smtpd_check_rules.  A typical default setting is shown ... "

This was taken from the following link:

http://no.longer.valid/phpwiki/index.php?pagename=How%20to%20restrict%20remote%20access%20to%20the%20SMTP%20server

Seems to me that editing this one file could solve the problem. I can´t find this file on my system. I can only reach /var/spool. There is no smtpd directory. I am using SME server 6.0

Could you please be so kind to help me ?

Thanks in advance

[Mumm-Ra]

First of all a check to see if your server is acting as a relay http://www.abuse.net/relay.html.
If it is, have you entered any other networks in the 'Local Networks' server-manager panel? i.e a network of 0.0.0.0 would enable the whole of the internet to use your server as a relay.

[duncan]

Hi,

Just because your ISP can telnet your mail server does not mean you are acting as a relay. This is completely normal behaviour for a SME server (and most other mail servers).

Your ISP is probably being over cautious. The link you are refering to is not really what you want (and is outdated).

Regards Duncan

[Mumm-Ra]

My isp actually tries to relay through my server about once every month, just to make sure I'm not an open relay.  I see it in my mail log files so his ISP may not just be telneting to his server but actually attempting to send mail through his server.
The link I posted my have bben there for years but it actually works and will give Roberto an idea if he is a relay.
Better to check that to leave it. He could even mail his log files to his isp to prove that he's not a relay if everything comes up fine.

[microlatina]

Hi again my friends !

Thank you very much Mumm-ra and duncan for the advice.
I did the test in http://www.abuse.net/relay.html.
The results were negative, meaning that my SME server cannot be used as an open relay though it can reply to certain commands using Telnet as duncan said.

I sent a copy of the results to my ISP.
I have learned something new !

This all started 2 weeks ago when a friend located in California and with an account with AOL told that he felt that something was wrong with my email traffic. I am located in Buenos Aires, Argentina. Most of my messages were considered SPAM. To make a long story short, my local ISP (a very big one) had loaded a black list from abuseat.org and they were blocking they own clients by blocking "neighbour dynamic IP´s"
I couldn´t send an email to my own account from my own ADSL connection !!!! I wrote to these guys abuseat.org and told them to explain my ISP how the list should be used, and finally I got unblocked. They confirmed that I had never been listed. Later an operator from my local ISP called me and told me that it was strange because he could Telnet my port 25, and you know the rest of the story.

Thank you very much for your help guys !