Actually, I believe this to be both more common and more legitimate than the comments received so far would suggest. This recognises that it doesn't make sense to ask for a review before the customer has even received the product, and a carefully-worded follow-up email expressing the hope that they are enjoying the product and inviting them to share their experiences of it can be a useful relationship building tool.

Some sites go even further and invite people to send in photos or videos of themselves using the products (not going to tell you which geeky sites I've been visiting - strictly for research of course!!!)

Alas, Zen Cart doesn't have much to help you in this area. I am working on something very similar for a client, but it's not necessarily directly applicable to other situations.

But here's an outline.

Create a CRON job to call a PHP script which will look for orders that have been delivered within a time range and break them apart to create a list of customers and the products they purchased.

Then extract a list of all reviews for these customers and remove any products that they have already reviewed.

Finally send the customers emails making reference to their products and inviting them to the come to the site.

The link they are given is to a new page (my reviews) for which they will need to login. This is also accessible from the main navigation menu.

The page lists all their reviews and also products that they have purchased but not yet reviewed, with a link to write a review.

This requires some knowledge of CRON or help from your web host and intermediate knowledge of PHP, MySQL and Zen Cart's internal architecture.