Can 2 primary mail servers act as backups for each other

hi guys,
just a general question…

is it possible for two primary mail servers to act as backup mail servers for each other?

I am assuming its mainly just:

  1. registering the opposite server in webmin> “webmin servers index” on both machines and,
  2. a dns issue and having virtual domains on both servers where in dns the relevant domains point the secondary mxrecord at the opposite server as the backup?

is that correct?

Is this a reasonably satisfactory efficient use of the backup mail server (ie to also put virtual domains on it for web and email hosting?) Just thinking about the need for a backup mail server but also money saving i suppose…so if one could also use the backup mail server for hosting other domains…?

Sure. No problem doing this, as long as they don’t host the same domains. i.e. you can’t make it like a backup for your Virtualmin domains and also make it a forward and hold secondary for those same domains (because you’d have two conflicting delivery instructions for those users…one would be to deliver locally and the other would be to hold/forward).

But, maybe just make a tiny server to be the secondary for all of your mail servers. Might be easier to manage.