Hi Fernando
Very much SAP Standard functionality in the WEB UI
Bit hard with the limited information you've supplied, but I'll assume you're using address dependant email addresses.
Go into page configuration and make sure the Address Assignment Block is visible.
From there click on New to Add a new address, within the view that is presented, you not only can add addresses, but Email Address, Cell Phones, Fax, etc.
Hope this helps
Regards
Arden