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.
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? Regards Ansgar Wiechers -- "Abstractions save us time working, but they don't save us time learning." --Joel Spolsky
