On Tue, Oct 25, 2011 at 12:29 AM, Dennis Burgess <dmburgess@linktechs.net> wrote:
I am curious about what network operators are doing with outbound SMTP traffic. In the past few weeks we have ran into over 10 providers, mostly local providers, which block outbound SMTP and require the users to go THOUGH their mail servers even though those servers are not responsible for the domains in question! I know other mail servers are blocking non-reversible mail, however, is this common? And more importantly, is this an acceptable practice?
Hi Dennis, Blocking outbound TCP SYN packets on port 25 from non-servers is considered a BEST PRACTICE to avoid being the source of snowshoe and botnet spam. Blocking it from legitimate mail servers... does not make sense. The SMTP submission port (TCP 587) is authenticated and should generally not be blocked. Regards, Bill Herrin -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004