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Test mail server for an open relay

I don't want let spammers take control of my mail server, I have configured my mail server but I am not sure how do I test my mail server for open relay? But what is an open mail realy?

An open mail relay occurs when a mail server processes a mail message where neither the sender nor the recipient is a local user. In this example, both the sender and the recipient are outside the local domain (or rather, the local IP range, for the technically inclined). The mail server is an entirely unrelated third party to this transaction. The message really has no business passing through this server.

I can check my server for open relay using any one of the following methods.

The old way (open relay server test)

Telnet to mail.myserver.com at port 25 and issue all the following commands:
helo client.server.com
mail from: rockyjr@vsnl.com
rcpt to: vivek@nixcraft.in
$ telnet mail.myserver.com 25Output:

Trying 202.51.x.xxx...
Connected to mail.myserver.com.
Escape character is '^]'.
220 mail.myserver.com ESMTP Postfix
helo client.server.com
250 mail.myserver.com
mail from: rockyjr@vsnl.com
250 Ok
rcpt to: vivek@nixcraft.in
554 : Relay access denied

As you see access denied to send email i.e. my mail server is NOT open relay.

The new way

Another and the best way is to use this website to test an open relay.

See also:

  • ORDB FAQ

This is an old post created by LinuxTitli but it was deleted accidentally by me :( I had restored the same from Google cache :)

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{ 11 comments… add one }

  • Sean October 27, 2006, 1:40 pm

    From your mail server, telnet to

    relay-test.mail-abuse.org

    It will do an extensive scan of your IP and immediately report the problems

    Sean

  • nixCraft October 27, 2006, 2:03 pm

    Sean,

    Good finding.

    Appreciate your post.

  • Czar October 27, 2006, 4:35 pm

    and if one would see “250 Accepted”… how does one stop an open relay

  • nixCraft October 27, 2006, 4:58 pm

    It is depend upon your MTA. For example postfix use following directives:

    smtpd_recipient_restrictions =
    permit_sasl_authenticated,
    reject_unauth_destination,
    permit_mynetworks,
    reject_unknown_recipient_domain,
    reject_rbl_client relays.ordb.org,
    reject_rbl_client list.dsbl.org,
    check_relay_domains,
    permit

    Sure you need to configure sasl authentication and maintain the list of virtual domains. Let me know your MTA name.

  • gofirefox October 27, 2006, 5:38 pm

    Good information, now i know how to find out if it is open

    thanks a lot

  • cc April 17, 2008, 2:01 am

    yes,i agree with,i don’t want get spam email too.great it’s useful for me.

  • Abhishek Dey May 29, 2008, 5:02 am

    hi i m trying to build an email site….but i get a rejected mail message when i send mails to rediff and yahoo. but i succesffully sent mails to gmail server and cooltoad server(cooltoad.com).
    Please can you tell me what could be the reason??

  • fosiul September 16, 2008, 3:21 pm

    check your IP here
    http://cbl.abuseat.org/lookup.cgi

    if your ip is listed here then it will be rejected by yahoo.

  • volkswagner January 8, 2010, 10:27 pm

    Sean, I tried to telnet relay-test.mail-abuse.org, but I did not see any automated results.

    I performed the instruction set for open relay test and got access denied.

    What should I get in response fro relay-test.mail-abuse.org?

  • arfie July 1, 2010, 3:26 am

    Hi,
    Do you want to know how to make qmail mail server become close relay?
    Because i think qmail is open relay so i often email from the spammers.
    I have configured tcp.smtp file like this:

    127.:allow,RELAYCLIENT=””

    but i still receive spam.

    And when i follow your instruction the result is still open relay.

    Thank you for your answer.

    • Amit May 5, 2011, 8:31 am

      Hi,
      use following
      127.:allow,RELAYCLIENT=””
      .:deny
      and run
      qmailctl cdb

      Regards,
      Amit

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