On 2011-06-10 Wiebe Cazemier wrote: > Ansgar Wiechers <li...@planetcobalt.net> wrote: >> On 2011-06-09 Wiebe Cazemier wrote: >>> I was setting up a fallback MX server with Postfix and was struggling >>> with preventing backscatter mail. I thought I found a good solution, >>> but it turned out to be an illegal option. >>> >>> Postfix has the ability to do recipient address verification. When >>> postfix acts as a relay server, this prevents backscatter mail >>> (bounces of messages because the server that is relayed to doesn't >>> accept the user). Backscatter is usually caused by spam of course, >>> because spam is sent to all kinds of users @example.com. >>> >>> I had in mind to use recipient address verification to avoid that and >>> then set "unverified_recipient_tempfail_action = permit". The idea >>> behind this was: >>> >>> - Prevent backscatter mail when the primary host is up because every >>> address is verified first. >>> - Accept all mail when the primary host is down, so that incoming >>> messages aren't deferred. >> >> Why? What issue in particular do you see with simply doing recipient >> verification (and rejection of messages to invalid recipients) on bot >> MXs? > > Well, when the primar is down, all incoming messages on the fallback > are deferred, because it can't do the verification. This means the > result is the same as having no fallback at all.
There's more than one way to do recipient verification. Use $relay_recipient_maps on the backup MX. And don't top-post. Regards Ansgar Wiechers -- "Abstractions save us time working, but they don't save us time learning." --Joel Spolsky
