From: Roland Turner [mailto:[EMAIL PROTECTED]]
>(Notes:
>- For those who don't follow, the problem is that having a single MX
>means that if that MX is down, the domain's entire mail
>service is down.
>- Telstra is not the only large ISP that exposes itself this way. I am
>not suggesting that Telstra is the world's worst, but that
>it's up there
>with them.
>- At least someone inside Telstra understands the risks associated with
>the lack of redundancy: telstra.com.au has two MXs.
>- It is likely that 139.134.5.153 has something comparable to a Cisco
>Director on it, and a farm of actual mail servers behind it.
>This is not
>enough, the Director and the network leading to it remain single points
>of failure.
>)
Just because there is a single IP address doesn't make it a single point of
failure. As you mentioned, it is possible to have a farm of mail servers,
though you forget that you can have multiple routes from the internet
channeling into the farm, with multiple Cisco Director style machines doing
the load balancing.
This is how your typical web server farm works. Mail servers are no
different.
John Wiltshire
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