Is your server running as an open mail relay?

There is a risk that your mail server could be used by a third party to send spam across the Internet.

As a BT Business customer, you need to check that your mail server is secure not set up to be an open relay.

Check that your server is not set up as an open relay:

  1. Create a separate connection to the Internet - not the same connection as your mail server. This connection can then be used to check your mail server.

  2. The easiest way of checking is to use Telnet to connect to port 25 of the public interface (IP address) of your mail server.

    The command needed to do this from a DOS prompt would be ‘telnet 25’ (where would be the public IP address of the mail server).

  3. Once connected to the public interface of the mail server, you will need to attempt to send an e-mail from an unknown user to an unknown user.

    To do this type the following in the telnet window - press Enter, or Return after each line:

    HELO (this is not a misspelling - the command does only have one 'L')

    MAIL FROM: user@

    RCPT TO: user@

    sendingdomain and destination should be valid domain names.

  4. If you get an OK response from your mail server then it is set to be an open relay.

    If the server is secure then you should see a Relaying denied error message.

  5. Type QUIT to close the connection to the server.


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