Load Balance 2 MTAs
Looks like this is a common question that never gets an answer but I'll try.
I want to set-up 2 MTA servers to handle the incoming and outgoing emails.
How do I load balance the email traffic to use both servers?
Is it a DNS record or is it in the MTA configuration?
Brad, in a multi-server install Zimbra will automatically balance outbound MTA servers. For incoming you'll need to use DNS balancing or an appliance that can balance.
I'm using my firewall to run an SMTP proxy that does an AV/SPAM filter and then passes the traffic to a load balanced NAT. I also balance between WANs (T1 and Cable line) as my MX1 and MX2 records to help availability.
I'm using Watchguard hardware, but this is a fairly universal process.
Hope this helps point you in the right direction.
Brad, the simplest solution can be DNS load distribution with two A records for your MX.
You may want to check out nginx documentation, AFAIK it can do load balancing too and is integrated with Zimbra.
As per above, that's essentially your two choices:
1) DNS round robin: you can do that by just listing two A records with the same MX hostname
2) AV/AS solution round robin (as with BareFootPanda, I use a separate AV/AS gateway in front of Zimbra, and it round robins with the number of MTA hosts I give it.