On 8/14/2013 10:21 AM, Grant wrote: >>> A few people have told me they received an email error message after >>> emailing me. I'm trying to get a copy of one of the error emails, >>> but I can't imagine what would cause that besides possibly my >>> greylisting. Has greylisting been known to lead to email error >>> messages being sent to senders in some instances? >> >> The sender may receive an error if their server has an unusual >> setup. Such servers must be whitelisted in your greylist software. > > The last sender who told me about the error message was on a > comcast.net address. I found this which describes the same problem > with greylisting and comcast addresses but the solution turned out to > be fixing the MX record: > > https://discussions.apple.com/thread/3030480?start=0&tstart=0
Nothing described in that posting indicates a problem with the MX record. Either the poster didn't describe the problem he found and fixed, or didn't understand the problem (the rDNS problem that was described is not a problem for receiving mail, but might affect sending). Comcast (nor any major provider) should be greylisted. Any reasonable greylist software should have a setting to whitelist well-known mail servers. > > My DNS is hosted by my domain name registrar and the MX record looks > like this (but with my real domain): > > Host Name: example.com > Mailserver Host Name: example.com > Mail Type: MX > MX Pref: 10 > TTL: 1800 > > Does it look OK? Yes, this is fine, and not the source of any problems. > It turns out I'm using postscreen with deep protocol checks: Postscreen will defer one mail once every 30 days per unique client IP. If that's not acceptable, turn off postscreen deep protocol checks or whitelist known good servers (from domain SPF records?) in the postscreen access list. Postfix 2.11 (currently in development snapshots) includes a wonderful feature to bypass postscreen tests for clients listed in dns whitelists, such as list.dnswl.org, greatly reducing unnecessary tests. -- Noel Jones
