SSH: Creating email, checking free disk space

[Allen Fan]

I have Cpanel mainly for backups (which can be done automatically with no license) and for creating/deleting email accounts.I'd like to learn those commands in SSH so that I don't have to pay any license. To be more specific, these are the commands I need to know:1)The directory that the emails are usually located.2)The command I have to run in order to create an account (account email, name and password).3)How to check free disk space for each of my accounts.Please explain in details because Iam a amateur SSH user.Thank you.