DNS MX Load Balancing???

[Barry Margolin]

In article <7l8ssp$uej$1 at nnrp1.deja.com>, CJS  <clifs at bigfoot.com> wrote:
>I would like to load balance 2 Mail Servers via DNS.  I now have my 2
>mail servers listed as MX records with equal priority levels.  Example
>below:
>
>mydomain.com      IN MX 1    mail1.mydomain.com
>mydomain.com      IN MX 1    mail2.mydomain.com
>
>However, I have heard that some Message Transfer Agents (specifically
>bind 4.x) ignore the second server unless the first is down.  Is this
>true and if so is this the best way to load balance mail servers?

BIND 4.x isn't an MTA, it's a DNS server.

RFC 974 says that MTAs must select among equivalent MX records randomly.
Most mail servers follow this rule.

However, even if they don't, BIND's round-robin scheme should result in the
order of the records being randomly distributed, so MTAs that choose them
in order will still result in load balancing.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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