I see their packages boast "business email addresses" for each package. Does this just mean as many that you can host if you already have a mail package? Or do these come with each package?

So say I get a package with 500 email addresses, is that just as many as it holds, or does that give me 500?

For that matter, is it restricted to one domain, or if I have multiple ones, can I use several different names with the package?

It's late, if you need me to clarify, please ask. Thanks for any help in advance.