Questions

Netcells Admin do not know or store your email box password(s).
However, you can easily re-set your email box passwords in your site's Control Panel (cPanel):
go to Mail > Email Accounts > click Change Password next to the email account in question, type/retype the password
Note that your local mobile phone's or computer's mail client (Outlook, Entourage, Mail, Eudora etc) will not be able to pick up mail from the server until you update its settings to the new password(s).

Accessing your site's control panel (cPanel) is explained in ›FAQ9