Re: Advanced tricks I use to get rid of spam using MX 4xx

[Marc Perkel <marc@perkel.com>]

Matt Thoene wrote:

Hello Marc,

Monday, November 27, 2006, 12:28:12 PM, you wrote:

  

That is correct.  Any MTA which immediately tries another delivery upon
receiving a temporary deferral is broken.


  
      

So - Qmail does it right and every other MTA does it wrong?
    

It's been a while since I've worked with Postfix but I am pretty sure
they too do not immediately try backups when they get a temporary
deferral. The mail is placed in the deferred queue and tries again
later.
  

Nope - Postfix will immediately go up the MX list trying all servers. I'm sure of that because I have a test account on a Postfix server and I often test it. Only Qmail - and no other MTA will refuse to retry the higher MX on a 4xx error. I originally came here to report it as a bug and figured that it was only in very old qmail versions. I'm quite surprized to find it was deliberate and there's a cult like attachment to the problem.