On Mon, 9 Jul 2007, Marc Perkel wrote:

> The idea behind this is that it requires the server be touched twice in 
> the proper order to get in. Spam bots try once and not in the proper 
> order. That's how the filter works.

Presumably you have some kind of white listing? Otherwise, Exim as a
sender will behave like this:

1. Try first IP
2. Temporary error - remember this
3. Try next IP
4. Accepted - message delivered
5. New message arrives
6. First IP hasn't reached its retry time yet
7. Try second IP

Will that be accepted?

If so, that's fine for a server sending from a single IP. What about a 
server that sends from different IPs (because it's implementing a number 
of virtual servers) but has a single set of retry data? In the above 
scenario, the second message could then be from a different IP. (There 
are servers that do this - facilities were added to Exim not very long 
ago to make it easy to do this.) 

-- 
Philip Hazel            University of Cambridge Computing Service
Get the Exim 4 book:    http://www.uit.co.uk/exim-book

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