Marky Yehezkiel (SNC) wrote, at 10/06/2008 10:17 PM: > I just wondering is there any way in postfix that can check port 25 of > sender is open or not.
Why do you assume that a legitimate relay must also accept connections on port 25? There's no requirement that an MX must also be the source of outgoing mail for a domain. The method you propose would reject mail from many large ESPs (such as Gmail) or a number of mailing list services.
