Ok I see now, setting the from address to an alias set up to the account.
In that case no, from your example you will only be able to choose the admin@ account. The from addresses you select from are derived from the mailboxes you set up in HTC mail. It is not a text box which you can edit but a list you select from.
The only way to do what you want is to set up an actual account for each of those emails, not aliases and then add each of them to HTC mail. not really what you were looking for though.