Re: [Exim] Secondary Mail Server/Looping

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Author: Philip Hazel
Date:  
To: Marcelo Moreira
CC: Steven R. Bourque, exim-users
Subject: Re: [Exim] Secondary Mail Server/Looping
On Wed, 20 Nov 2002, Marcelo Moreira wrote:

> Then insert a MX entry like this:
> domain.com MX 15 10.10.6.70


NO, NO, NO, NO!

You should NEVER put an MX record like that into the public DNS.
Think about what will happen if a foreign host accesses those MX
records, and it has its own local network that is using 10.x.x.x
addresses. That is a disaster.

Almost as bad is the foreign host that isn't using 10.x.x.x, because it
may keep trying the address, and time out every time. This is wasting
other people's resources and therefore anti-social.

The only IP addresses that should appear in publicly accessible DNS
zones should be those that you expect foreign hosts to be able to use
for real.

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