Can you tell me what is a "Vanity" Email address
Sorry, this is a confusing term - a better description would be "email alias".
An Alias is simply a forwarding address.
You have unlimited aliases to one default address - this default address is initially setup to be your mailbox here on this system...
But you can change it to be any email box you want - you can have *@yourdomain forward to your AOL account if you like.
All email addresses *@yourdomain.com will forward to your default address. If at any time you would like this default address changed, login to Plesk, click on the domain you want to change default forwarding for, then click on "Preferences". The "mail to nonexistent user" field is where you should enter your default address
IMPORTANT: Be sure that you have "mail to a nonexistant
user" pointed at a valid email address! If you point it at an
email box that you no longer have, or an email box that
you haven't created yet, all your email will bounce.