efa-project.org

Update: so I installed a new system, but this time configured using the web interface...

This time, unbound starts and the /etc/unbound/conf.d/forwarders.conf file contains my 2 x internal DNS:
forward-zone:
name: "."
forward-addr: 192.168.10.31
forward-addr: 192.168.10.32
The contents of /etc ...

The console.

I installed a new system running CentOS 7.8.2003, over PXE using build script 20190323.
It rebooted and I logged in and ran through first-time configure.
I selected non-recursive DNS option, entered my 2 x internal DNS IPs (which both showed on summary screen).
The system rebooted again, I logged in ...

Would be better to replicate the DBs (with something like Galera) on each EFA to have a shared-nothing solution, otherwise DB is SPOF.
Then we could load-balance incoming email to multiple EFAs.

I don't think so, you can only specify one destination in postfix.

If (or rather when) your Exchange server crashes, you would have to change the IP in postfix, unless you use a DNS entry, in which case change your DNS to point to your Linux box.

The "parallel approach" is something I've been ...

Actually, I may have found a possible solution:

https://gitlab.dls-belgium.eu/tools/smptdd/tree/develop

Could this be implemented in EFA?

I have a requirement to send all incoming emails via EFA to multiple backend mail servers.

There's only an option to specify one mail server under Transport settings.

I guess this might be a postfix limitation?

domain.com smtp:[192.168.1.1]

I could use DNS RR, but then half the mail goes to one ...