(?) [email protected]? or [email protected]?

I have a domain on a hosting account.
I intend to create a subdomain, which is easily accessible by my domain.
The subdomain will be mail.mydomain.com.
I'll install an email php script on subdomain mail.mydomain.com.
When users create accounts at mail.mydomain.com, will their email addresses show:
[email protected]
or
[email protected]

???


I, of course, would like for their email addresses to be [email protected], for simplicity purposes.

Probably [email protected]
Although, the email script should specify this, or the guide (if any) that comes with it should say.