If customers purchase from you online, you need to send immediate order confirmations via email.
Think about when you go to the grocery store. You hand over your cash or credit card and immediately are given your products and a receipt. These are physical reassurances that your transaction is complete and you can go home happy.
In the online world, there are no such physical assurances. Often customers have to wait for a product to ship and fall into a limbo state of waiting for some confirmation that all is well.
During this waiting period, customers can be unsure of what happened or is happening with their order. This doubt and fear leads to an unpleasant buying experience that customers won’t be fond of repeating.
Your site may show an “Order Successful” type page after the checkout process is completed. However, this is not enough.
Let’s look at two examples.
When I place an order on amazon.com, usually by the time I’m done reading the summary page of my completed order, I’ve got an email from them confirming my purchase. By confirming my order in two places, on the original screen and via email, the retailer reassures customers that everything is fine.
Contrast this with when I place an order from Lego’s online store. It takes several hours after my order is submitted for me to get an email confirmation.
If your website has the technology to handle online orders, it can handle sending immediate emails to customers after the sale.
Reassure customers that the order went through and ease their anxiety by immediately confirming their purchases. If your company has slower, legacy systems that process orders coming from your website, send a confirmation that the order was received.
The key is to keep the customers in the loop of what is happening so buyer’s remorse doesn’t set in and lead to future problems.

It’s funny, I placed an order over the telephone and didn’t receive my email invoice until 3 days later! I called them hours later, just to see if they were in fact real.
@Demetrius – Timeliness is everything. Your example is another great one of where a customer’s fears start to creep in if immediate confirmations are not given.
Very smart advice. Companies need to take care with these auto-responder emails though. It’s important to handle them with care. Email, in general, can be a real sticking point with customers. Watch out for horror stories like this one – http://www.upyourservice.com/learning-library/customer-service-contact/whos-answering-your-email.
Yes E commerce sites should send automatic order confirmation and payment emails to clients for their assurance it also helps to increase returning clients.
@Josh – I agree: reassuring customers at the point of sale is a great way to establish the trust needed to have those customers purchase again.