[Greylist-users] Exploring Greylisting - Initial Block Time

hector santos hsantos at isdg.net
Thu Mar 2 11:54:49 PST 2006

Hi, I'm new to the list.

I have been exploring greylisting for our SMTP package.

I have a question regarding the recommended 1 hour initial block time.

I don't see the direct correlation of the block time with associating good
or bad SMTP clients.  The RFC has a recommendation, but that's just it - a
recommendation.  There is no fixture on a retry pattern, atleast I don't see

Isn't the primary goal satisfied by simply addressing the nearly 100% bad
actors that do not follow 421 response codes?

I have been exploring this with no block time limit. I'm close to putting
this out to beta testing and I'm wondering what default I should use.  It
seems to me that from an operations standpoint, we are a lot "safer" to not
have initial 1 hour block limit.  For our test site, I see just a
significant amount of good systems retrying within minutes or seconds.

I'm aware each site will have its own experiences.  Most of customers are
commercial oriented so this is one reason we were reluctant to offer
Greylisting in the past.

Overall, for our test site, I'm seeing around 64-68% success rate
(non-retries/total).  Do you think we might see a higher success rate with a
1 hour block time at the expense of raising some support issues with "good"
people trying to send mail with less than 1 hour retry frequencies?

Comments?  Experiences?


Hector Santos, Santronics Software, Inc.

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