On 5/16/2012 2:07 PM, James Lay wrote: > On May 16, 2012, at 9:42 AM, Ansgar Wiechers wrote: >> The answer to that question can be found in "man 5 transport". >> However, you don't want to mess around with a reject-users table in >> the first place (particularly not as a transport map). Instead just >> change your smtpd_recipient restrictions like this: >> smtpd_recipient_restricitons = permit_mynetworks >> reject_unauth_destination reject_unlisted_recipient ... As Brian >> already explained, it's the default to reject undefined recipients, >> so you wouldn't need to do anything (unless you have configured a >> catch-all somewhere, which you shouldn't). However, I consider it >> good practice to reject mail for invalid recipients early on (before >> doing more expensive checks), which is what the >> reject_unlisted_recipient restriction is for. Regards Ansgar Wiechers > Thanks Ansgar, > > I was under the impression that DISCARD was better then REJECT due to > backscatter? We get hundreds of crazy emails to things like > ya64s...@mydomain.com, so I opted for DISCARD instead. I'll do some more > reading and see how I can get this to fly. Thanks again. >
Definition according to Wikipedia: Backscatter (also known as outscatter, misdirected bounces, blowback or collateral spam) is incorrect automated bounce messages sent by mail servers, typically as a side effect of incoming spam. Backscatter occurs when you ACCEPT the message on the front end and then generate a bounce because it cannot be delivered. You want to flat out reject what you cannot deliver, that is the correct way to handle things. If malware, bots, or other trash is sending it, no one cares because your system will NOT generate a bounce. If it is a legitimate message, the SENDING MTA will bounce back to its user for notification. In some countries, I hear that it is illegal to discard email and reject is the only option. Brian
