Good question. This is (partly) also bound up with my earlier question on June 2. Sorry if I am stating the obvious, as I am still working my own way thro this, but did you find the Mail in the control panal, left column? Since you have a domain, I assume you start with Manage Email; but there is also a Web mail; I am not sure what are the differences.
If I find anything else I'll post again.
Also check MX mail xchange in the same column. See the DH wiki for more info.