Yes, I entirely agree.
However, clients don't see the technical side of things and a delay
of 10-15 mins is a disaster to some.
with postgrey/postfix:
the reject/delay happens once per triplet. A retried triplet gets
cached for 30 days (or as long as you set the cache parameter), so as
long as that triplet gets sent once per 30 days, there is no further delay.
3 different triplets retried gets the IP and its subnet permanently
excepted from greylisting. (another param that you can set at 2 or even 1)
We have lost clients because of this 'small' delay who see email as
an instant communication medium. Perhaps our arguments weren't effective enough
Perhaps your greylisting program wasn't as sophistcated as the one I use.
We tread the fine line between delivery and responsiveness and are
often found wanting but that is not our fault, given the nature of
email and its potential for exploitation.
Exactly, there are so many other reasons that mail gets delayed.
There are extreme, pathological cases that greylisting bothers. eg,
legit servers that aren't RFC-compatible and simply NEVER retry after
seeing a 4xx reject, or servers that retry 12+ hours after a 4xx
reject. Of course, such servers will have the same problems with
1000s of other MXs that now do greylisting.
The chances of any specific MX actually seeing one of these
RFC-incompatible nutjobs is extremely small. And often an alert ISP
who knows his clients will know the client who erroneously expects
guaranteed real-time inbound mail delivery email and the servers he
expects that from, and can whitlist them in advance.
And if mail from these servers is so darn real-time critical, why
aren't these servers retrying 4xx rejects at all, and why not
retrying in less than 12 hours, in the first place? Not to use such
a powerful policy as greylisting because a miniscule number of
RFC-violating servers is pretty silly.
Len
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