If you have mail that is getting blocked by greylisting, you have a 
problem with your mail relay.

Greylisting looks at one or more of these items:  envelope sender, 
envelope recipient, and IP address.  I happen to look at all three on the 
spam filters I run.  The first time the combination of examined data is 
seen, a temporary failure is returned during the SMTP connection.  The 
information is stored locally on the receiving system to be checked for 
the next time the message is sent.  Some older ratware does not bother to 
retry, so the spam/virus is not delivered - that's good.  Some broken 
mailers also don't retry - that's bad.

In over a year of using greylisting for 28,000 accounts and 35+ domains, 
I've only run into two problems.  One was a competing list management 
software (Lyris) that delivered index versions of the list fine, but puked 
when the user requested an article.  I never got an answer from the list 
owner/site manager on what was happening.  The other was a Trend Micro 
system.  My filters wait until after the data phase because some mailers 
like Groupwise fail to deliver if they get tempfails on all recipients. 
With this particular system, it was deleting the message file as soon as 
it completed sending the data, even though it was temp failed.  The mail 
administrator worked with Trend Micro and quickly received a patch that 
addressed the issue.

I have not heard of any issues with sendmail having problems with 
greylisting, but it could be a configuration issue.  One thing you might 
look into is how often you have sendmail retry the delivery.  Most 
greylisting implementations require a certain time between delivery 
attempts.  I used to use 5 minutes, but  have dropped that to 2 minutes. 

---

An electronic message is "spam" IF: (1) the recipient's personal identity 
and context are irrelevant because the message is equally applicable to 
many other potential recipients, AND (2) the recipient has not verifiably 
granted deliberate, explicit, and still-revocable permission for it to be 
sent, AND (3) the transmission and reception of the message appears to the 
recipient to give a disproportionate benefit to the sender.  -- 
http://www.mail-abuse.com/spam_def.html


William Brown
Messaging/Filtering Services
Technology Services, WNYRIC, Erie 1 BOCES
(716)821-7285


"LISTSERV site administrators' forum" <[log in to unmask]> 
wrote on 04/20/2005 11:22:46 AM:

> Do the various components in listserv work properly with sites that 
> use greylisting?
> 
> message delayed, see <http://projects.puremagic.com/greylisting
> >http://projects.puremagic.com/greylisting ; Please try again later
> ...
> 
> Their site says
> 
> "The reason your mailserver is getting blocked is most likely that 
> it does not properly handle 45x SMTP error codes, and does not retry
> delivery within a reasonable amount of time after receiving such a 
code."
> 
> This would not directly involve listserv but could be a problem with
> our sendmail.