Re: [Exim] offers123.net & possible DOS.

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Author: Philip Hazel
Date:  
To: David Woodhouse
CC: exim-users, Dave Restall
Subject: Re: [Exim] offers123.net & possible DOS.
On Fri, 17 May 2002, David Woodhouse wrote:

> {For how long,} does Exim cache the result of such a callback?


Only for the one incoming process.

> If I do this on a box from which 3 people are subscribed to a list like the
> linux-kernel mailing list, how many connections per day will it be making
> to verify owner-linux-kernel@...?


Far too many. Callback was implemented as an experiment. It now seems to
growing in popularity. The Exim 4 wish list contains this item:

(2) 01-Jan-02 S Cache callout information

This could result in very large databases, because the cache would have to be
keyed on IP address plus sender (or recipient) address.

Unfortunately, I won't be doing much Exim development for the next few
months, until I have completed work on the next edition of the book.


--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.