You'll have to delve into the mysterious world of SSH (<b>S</b>ecure <b>SH</b>ell).

I once needed to have a FirstClass mail server execute a script on a remote backup server to start a daily backup process. A script on the FirstClass server first paused its mirrored mail-store disk, did some sanity checking to make sure the pause actually occurred, (backing up the live mail-store was a recipe for disaster), then used SSH to execute the script on the backup server to start the backup job.

The backup software then conveniently ran a post-job script which, through SSH to the FirstClass server, un-paused the mirror mail-store disk. Once I got the SSH details figured out, (the Secure part was the tough nut), it worked like a charm for years until Google took over and we had to drop FirstClass.