Test for open relay

[skeating]

How can I test if my firewall is being used for an email relay? I have landed on a couple of block lists, with the IP for the firewall being listed as the culprit. There is a mail server behind the firewall, and I have tested that and confirmed it is not relaying. That only leaves the firewall to be checked.

Stephen Keating

[dotdash]

Unless you installed postfix, it's not going to be the firewall. Probably some kind of spam mailer on a workstation. Add a rule to allow outbound smtp from your mail server, then block and log all other smtp traffic from the lan.

[skeating]

Thanks

[KOM]

MXToolbox has a bunch of tools, including an open relay test during its diagnostics:

http://mxtoolbox.com/

http://mxtoolbox.com/diagnostic.aspx