[BlueOnyx:01257] Re: SMTP Relay servers

[Colin Jack]

> Realistically, the idea is a non-starter.  The problem you will run into
> is that the end-user's ISP will cache a lookup.  Then of course the
> client machine will do a lookup and resolve the hostname to the IP.
> Then it will cache.
> 
> Then if one of your SMTP boxes dies for some reason, anybody who had
> already been using that would be down, but the other customers that
> achieved the lookup to another box would still ostensibly go through.
> 
> Sure, you could monkey with TTL's and expires, but then you're creating
> more overhead on your end with all the lookups, and there's the added
> issue that in order to reduce network load many of the larger ISPs
> completely ignore your TTL and expire times and cache for whatever time
> period they see fit.   This appears to be an increasing trend.
> 
> The better idea is just to have your SMTP not "go down", and if you're
> really concerned, or you have a history of flaky SMTP boxes, have a
> warm-spare standing by.
> 
> Alternatively, you could set up some fancy NAT-based load balancing at
> your server-side.
> 
> But DNS is not an ideal way to handle this.
> 
> --
> Chris Gebhardt
> VIRTBIZ Internet Services

Cheers Chris - that was my gut feeling I suppose - just hoped somebody had a clever idea!

We don't have a history of SMTP boxes failing (touch wood) but sometimes they can get busy with a spam storm or suchlike, so it was just an idea. 
Also in the event that it does go down it gives us some breathing space.

Ho hum

Colin