The mail tab under Settings displays the following fields:
Mail Protocol: Lets you choose between sending mail to the host's email, or through an SMTP. You should contact your shop's hosting provider to see if configure PHP mail. If not, you need to use a SMTP, such as gmail.
Mail Paramaters: Asks for the e-mail address for the store if "Mail" was selected under Mail Protocol.
SMTP Host: The address of the smtp host.
SMTP Username: The full email address for the SMTP host
SMTP Port: The port number provided by the SMTP host.
SMTP Timeout: A timeout number provided by the SMTP host.
New Order Alter Mail: Selecting 'Yes' will send a notification email for every order submitted in the store front.
New Account Alert Mail: Selecting 'Yes' will send a notification email for every account created in the store front.
Additional Alert E-mails: List any additional e-mails that should also receive the notification emails above.