Hello pvtpyro,
You will need a custom module or reg. script hack for what your asking for, because neither XOOPS or the typical mail client has the administrative capabilities to create e-mail accounts.

Due to the combination of mail clients provided I'm thinking you might have a cPanel hosting account, since those three are typically used with cPanel. Do you have cPanel? I can hack your reg script if so. I will be needing a similar script myself within a few weeks for a project that I am going to be starting so won't be a setback.