MailScanner on a cluster

[Julian Field]

Dave Strydom wrote:
> Please excuse my ignorance, but can anyone point me in the right 
> direction of:
>
> a) is it possible to run MailScanner on a cluster
Yes.
> b) If so, can you please point me to some documentation so i can read
> up on it please.
It's very easy.
At the simplest level, which actually works remarkably well considering 
how cheap the solution is, is this:

Solution 1
===========
Create a new DNS record called mx.yourdomain.com and assign multiple 
'A'records to it, one for each of the IP addresses used by your cluster 
of servers.
Put a single 'MX' record in your domain's DNS records, pointing to 
"mx.yourdomain.com." (Don't forget the "." on the end).

@        10 IN MX        mx.mydomain.com.
mx       IN A          192.168.99.101
            IN A          192.168.99.102
            IN A          192.168.99.103
            IN A          192.168.99.104
            IN A          192.168.99.105

It's as simple as that. The DNS lookups will rotate through the members 
of your cluster, spreading the messages (by quantity, not by size) 
across your cluster.

Solution 2
===========
You can also do this by having multiple MX records all with the same 
priority number, each pointing to mx1, mx2, mx3, mx4 etc.

@        10 IN MX        mx1.mydomain.com.
           10 IN MX        mx2.mydomain.com.
           10 IN MX        mx3.mydomain.com.
           10 IN MX        mx4.mydomain.com.
           10 IN MX        mx5.mydomain.com.
mx1       IN A          192.168.99.101
mx2       IN A          192.168.99.102
mx3       IN A          192.168.99.103
mx4       IN A          192.168.99.104
mx5       IN A          192.168.99.105

Some people argue that this is better as it is more likely to deliver 
mail quicker when you take some of your servers out of action. They are 
possibly right.

Solution 3
===========
You can also do this by spending a fortune on Cisco load balancers and 
have heartbeat monitoring systems, etc. But it won't make any big 
difference, but you will have a very expensive Cisco box to look after 
and a big hole in your bank balance.

Again, can someone please put this in the Wiki for me?

-- 
Julian Field
www.MailScanner.info
Buy the MailScanner book at www.MailScanner.info/store
Professional Support Services at www.MailScanner.biz
MailScanner thanks transtec Computers for their support

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