Email server backup

Im loosing my mind here.

I currently am using a FEDORA CORE linux email server.

Problem: I need received & sent emails of all employees to be backed up.

All employees use Windows operating system. I need to be able to give them their sent and received emails anytime on demand. What do i do now? Im not a linux expert, and our linux server is physically located in canada away from me…it is remote.

Shall i make a new windows email server physically located with me??? Problem is i dont have a stable Internet connection here with me, what if it fails? what backup do i have?

The current linux system is very reliable, uptime = 99.9%

I need to somehow back up all their mails.
Any ideas?