From PhpCOIN Documentation
There are four email contacts by default within phpCOIN. When you installed it, phpCOIN took a pretty good guess what the addresses would be for you, but you may need to change these to match your actual email addresses.
Click [Admin] and then click [eMail Contacts] under the 'Email' Section. Select the address you want to change from the drop-down list.
Name: How the name will appear on listings such as the "Contact Us" form. Email: The actual address to send email to Status: Whether or not this email address is enabled (available for use).
phpCOIN requires the four built-in addresses named 'sales', 'webmaster', 'billing' and 'support'. They may all point to the same actual email address if you want, but the specific names must exist because phpCOIN looks for specific names when sending certain emails.
You may also choose to add additional emails to the system. They will be made available for the To field on the 'Contact Us' form, and to the From field on the 'Email Client' form