What are the partitions created on the mail server hard drive?

The main partitions are done firstly which are root, swap and boot partition.

But for the mail server three different partitions are also done which are as follows:

1.  /var/spool - This is done so that if something goes wrong with the mail server or spool than the output cannot overrun the file system.
2.  /tmp - Putting this on its own partition prevents any user item or software from overrunning the system files.
3.  /home - Putting this on its own is useful for system upgrades or reinstalls. It allow not to wipe off the /home hierarchy along with other areas.