Rolf E. Sonneveld wrote:
The problem here is that the greylisting mechanism used by Getronics
remembers the connection attempt for only one hour.
That greylisting mechanism is broken, then. Getronics should change
Greylisting is unfriendly, so greylist implementors should do
everything in their power to mitigate collateral damage. Our
greylisting implementation remembers greylisting details for 48 hours.
In addition, once an SMTP host has passed the greylisting hurdle, we
disable greylisting completely for that host for 40 days. (A host
that retried once is very likely to retry every time, so further
greylisting is pointless.)
Even so, we do not enable greylisting by default; our customers have
to turn it on if they want to use it.