the Greylist specs shows a 4.7.1 extended code:
451 4.7.1 Please try again later
I believe that the reply code mentioned in that whitepaper is
incorrect. The extended code is correct. I recommend using "450 4.7.1
Text" when the temporary failure is due to a policy decision.
Incorrect in what way? Inappropriate perhaps from a "operator/policy"
statement? Functionally or Technically? Compatibility? If its a
compatibility problem, then it needs to be reconsidered.
As a general rule, I would use 30 minutes as receivers reading RFC 2821
will expect that.
Sure, but all receivers need to be ready for anything, including the
possibility of "more sophisticated and variable strategies" as it was
insightfully stated in 2821. :-)
So I don't think its would be a technical problem.
Hector Santos, CTO