Brian Evans - Postfix List wrote: > Mikael Bak wrote: >> Brian Evans - Postfix List wrote: >> >>> Mikael Bak wrote: >>> >>>> Santiago Romero wrote: >>>> >>>> >>>>> Really, reject_unverified_recipient feature is very nice, but rejecting >>>>> all mail when primary MX doesn't answers breaks it for us :( >>>>> >>>>> Any idea? :? >>>>> >>>>> >>>> Hi, >>>> >>>> Quoting the documentation[1]: >>>> >>>> "The unverified_recipient_defer_code parameter (default 450) specifies >>>> the numerical Postfix SMTP server reply code when a recipient address >>>> probe fails with some temporary error. Some sites insist on changing >>>> this into 250. NOTE: This change turns MX servers into backscatter >>>> sources when the load is high." >>>> >>>> So you are not rejecting any email if the MX is down. You are just >>>> delaying reject or accept until the MX is asked if there is such user or >>>> not. We're very happy with this over here. >>>> >>>> >>> No, you are not "delaying reject". >>> You are bouncing and possibly BackSattering because you really don't >>> know if the recipient is valid. >>> >>> Many, many envelope recipients are forged these days. >>> So you end up bouncing to the wrong place and sending spam to a 3rd party. >>> >>> A good MTA in the world will hold a 450 for 3 to 5 days and keep retrying. >>> If it doesn't retry, it's usually a bot and bad for your health. >>> >>> >> Hi Brian, >> Well, thank you for sharing this with me. >> >> IMO this setup does not bounce as you say, it sends a "450 Address >> verification in progress. Try later.". When the client tries next time >> there is either an OK the address exists, or a 550 User does not exist. >> >> Maybe I don't understand what you try to say. I just don't see why this >> would generate bounces or backscatter. >> >> Mikael >> >> > I was referring to the "change to 250" that was quoted. > I inferred that was the advice being given. > > If this was incorrect, then, yes, it is just fine to use.
Hi Brian, I knew that we were misunderstanding eachother. :-) So to clarify. We have the unverified_recipient_defer_code parameter set to its default (450). Mikael
