I run WBL (same as RH ES) with sendmail 8.12.10 and MailScanner with ClamAV, spamassassin and am 100% sure the box does not allow relaying (unless authenticated).
I would like to test my box for open proxies, and if I find any, how to block/close it.
I found a util (perl script) that runs test against any machine, but either I am not passing the correct arguments, or there simply are no open proxies, yet some of my users claim not being able to send to yahoo addresses - Yahoo says the box has either open relay or open proxy. I've followed their suggestions and checked the box against Open Relay and other spam db's, no hits...
Anyway, I want to make sure for myself, so I would appreciate links to sites that have tools as well as some examples of running the tool ( if command line tool) .