Vishal Kothari

This plugin validates the existence of the domain name that is entered in the email address while checkout. This plugin strengthens your email validation by more than just the regular expression matching, thereby reducing chances of loosing an order due to incorrect email address & increasing accuracy of your data.
The checkout process cannot be completed till the email address is entered with the correct domain, thus eliminating any chances of a wrong email address (at least the domain can’t be wrong).
If the domain is not a valid domain, it will show an error and not allow the customer to checkout till the email address is entered with the correct domain.
Other free plugins for WP e-Commerce:
<ul>
<li><a href="https://wordpress.org/extend/plugins/viral-coupon-for-wp-e-commerce-lite" title="Viral Coupon Plugin" rel="ugc">Viral Coupon Lite for WP e-Commerce</a> – Social Media Promotion Tool for your store (Facebook)</li>
<li><a href="https://wordpress.org/extend/plugins/order-delivery-date" title="Order Delivery Date" rel="ugc">Order Delivery Date</a> – Allow customers to choose their order’s delivery date</li>
</ul>
Premium plugins for WP e-Commerce:
<ul>
<li><a href="http://codecanyon.net/item/viral-coupon-for-wp-ecommerce/2644621" title="Viral Coupon Pro" rel="nofollow ugc">Viral Coupon Pro</a> – Promotes your store on Twitter & Google+ in addition to Facebook.</li>
</ul>

Email Domain Checker for WP e-Commerce

This plugin validates the existence of the domain name that is entered in the email address while checkout for WP e-Commerce store owners.

Warren Harrison

The User Domain Whitelist/Blacklist plugin limits user registration to only registrants with an email address from the domain white list below OR prevents registrants with an email address from the domain black list below from registering. For example, hortense@example.com would only be allowed to register if example.com appeared in the domain white list. Conversely, hortense@example.com would not be allowed to register if example.com appeared in the domain black list. Anyone attempting to register using an email address outside the white list or inside te black list will receive the error message below.Anyone attempting to register using an email address outside the white list will receive an error message. Both the domain whitelist and the error message can be modified via the plugin options page (available under the Settings menu).

User Domain Whitelist

The User Domain Whitelist/Blacklist plugin limits user registration to only registrants with an email address from the domain white list provided by t …

Email Domain Checker for WP e-Commerce vs User Domain Whitelist