John Levine wrote:
For a while I used a very aggressive greylister which soft failed after the dot, kept a hash of the message, and wanted to see an exact copy with the same hash to let the message through. I stopped using it, but not because of SMTP problems. (A surprising number of ESPs reconstruct the message rather than retransmitting it, so the hash didn't match.)
Yes. And unlike bots, ESPs will do retries. (Lord knows they do retries, even on 550 errors.) At Habeas I had a customer that set the Date field at connect time and generated no Message-ID field at all; and they complained to /us/ when we logged duplicates!
I haven't seen that problem as much as I used to, though. As the volume demands on the have grown, the software developers seem more inclined to do more computation in advance and less at delivery time.
<csg>
