[clug] spamsum usage in the real world

[Jacinta Richardson]

Kim Holburn wrote:

> You can grey list with a 30 second delay if you want.  It doesn't  much
> matter.  Grey-listing shouldn't cause much delay at all.  Of  course I'm
> not sure it's much use either.

As far as I understand things, the delay from the mail receiver side is
largely irrelevant.  The delay is actually an issue from the senders
mail server.  What happens is this:

	Client's mail server sends email to receiving server
		Server says "I'm busy, please try again later"
		Server continues this for 30 or so seconds
		Server then records the attempt and waits for resend
	Client's mail server receives I'm busy and waits some time
	Client's mail server's wait times out
	Client's mail server sends email to receiving server
		Server accepts email

The reason this works (or did) was because Spam servers typically didn't
respond correctly to the "I'm busy, come back later".  In fact there are
real mail servers in use "out there" that don't respond correctly
either.  Some try resending immediately, and then give up and silently
throw the mail away if unsuccessful, and some just throw it away without
ever retrying.  This used to be an argument against greylisting, but it
doesn't get as much mention anymore.


Anyway, the point is that the delay can actually be quite noticable.  On
our servers we usually assume it'll be about 20 minutes.  For us clueful
(and busy) folk this isn't usually an issue, but for people who like
everything to be instantaneous, 20 minutes is *forever*!

All the best,

	J