Interaction between greylisting and persistent host status

Gary Mills mills@cc.UManitoba.CA
Mon Nov 17 20:00:41 UTC 2003


I recently set up greylisting on my test mail server to give
it a try.  To test it, I sent a message from my production
mail server.  The test server rejected it with a temporary
SMTP response, just as it should.  However, the production
mail server uses a sendmail feature called `persistent host
status'.  Therefore, it marked the test server as non-responding,
and did not retry delivery until after a timeout period, three
hours in this case, had expired.  Only then, was the message
accepted by the test mail server.

The persistent host status feature is extremely useful to
streamline queue processing on a large mail server.  Without it,
almost all of the queue runner time is spent waiting for connections
to time out.  This makes it impossible to process a large queue
in a timely manner.  Setting the host status timeout to a value
larger than the slowest queue processing time solves the problem.

So, the question is:  How to make persistent host status interact
nicely with grey listing?  I'm not concerned about mail servers
at my own site, so much as other mail servers that may be using
either persistent host status or grey listing.

The other question is:  Is the SMTP temporary failure response
a server property or a recipient property?  In the former case,
persistent host status should mark the host as non-responding,
but in the latter case, it should not.

-- 
-Gary Mills-    -Unix Support-    -U of M Academic Computing and Networking-



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