Two mail servers, need help with dns configuration for the backup one

I need to run a redundant backup mail server in case the main one goes down.

The settings in GoDaddy look something like the following:

A (Host)

Host    Points to

@       ip address of mail1 41.x.x.x
mail1   ip address of mail1 41.x.x.x
mail2   ip address of mail2 196.x.x.x

MX

Priority    host         points to

10               @           mail1.mydomain.com
20               @           mail2.mydomain.com

When mail1 goes down, mail2 is able to get emails. I can access it through the browser with no problem, but I want my users to able to pop3/smtp as well without changing anything in their outlook. I dont want any impact to the users when mail1 is down.

Also, I'm using the windows server DFS to keep both folders of the mails in sync. Is this the right way, or should I be using something else?

Your DNS setup is OK to get redundancy on the "receiving" part.

The problem of syncing the mails still persists. I don't know how you are solving this. I even don't know if your server software is able to handle the situation that a user could purge the mails from one server while the other still delivers to the mailbox and simultaneously the syncing process copies mail from one to the other.

Nonetheless you still need to switch the POP3 server in case of a fault. Or how should they know that their POP3 server is changing from mail1 to mail2?