Maybe I can lend a hand here as I just explained this to a client.
you have your master domain. lets call it abc.com now abc.com has it own DNS and its own mail, and its own FTP.
Now you just went out and bought abc2.com because you like the name and its just cool to own more than one domain name.
However you want abc2.com to point to the same site that abc.com is.
Well for this you park the domain.
Once parked anyone who goes to abc2.com will see the same site as if they typed in abc.com
Mail in Cpanel can be set up to like the 2 domains. so firstname.lastname@example.org
In Cpanel when you add email you will have the option to pick the domain that the mail account is for.
I currently have 4 clients using this option and aside from Cpanel getting picky with DNS at first it works well.
If you need two seperate domains, and want to share the space and bandwidth ask your host for the option to use Addon domains, there may be a charge for this but it will allow to share space and bandwidth for two completely different sites.
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