Bill,
The only thing that I really need to replicate is user account details(username and passwords), so people can atleast POP into their account and send mail if the primary goes down. As of right now uptime is not an issue, but I really want to prepare for something that knocks the server offline for extended periods of time.
The inboxes of the actual users arn't really a concern, as most of them use POP and take their messages off the server as soon as they POP in.
The information would be replicated once a night by simply dumping the MySQL data and then transferring the MySQL dumps over to the backup server. I guess I am asking if the vpopmail MySQL database is the only thing I need to "sync" up with the backup, or is it necisarry to copy the entire domain folder for each virtual domain?
Your secondary MX setup is really all you need for backup, if your primary dies then the secondary queues the incoming mail until the primary is back up. Yes you should save a backup of the vpopmail domains folder, etc. but you can't run mail for a domain on 2 seperate vpop servers all the time.
Remember that if your primary fails you have a week to get it back online before the secondary will start bouncing mail back, that should be plenty of time to restore the server. I do this for a cable ISP who went offline for a week due to forest fires, their email was stored on my secondary system for them, I also had a copy of their vpopmail system and if the outage was going to last longer than a week I would have enabled it on the secondary, but it wasn't setup to do so automatically.
Secondary MX is your failover device, keep a copy of the vpopmail stuff there but don't try and get it to vpop deliver there when the primary is down, keep it there only in case the primary is down for extended periods beyond 7 days, although that type of situation should rarely happen. The customers can live without checking their POP3 every 5 minutes, just assure them that your system is continuing to spool incoming mail for them and it will get delivered once your primary server is restored.
For syncing your backup vpop, I usually copy the entire domains folder, and since you're using MySQL you should take a dump of that as well and store it on the secondary. You shouldn't run it live on the secondary server though.
John
