How to make purchase without registration

In the last two days new customers tell us they are not getting " password/activation link" emails to complete their registration so they can complete the purchase. Is there a way to set up the store to make registration optional? Make a purchase as a guest? If new customers are not getting the password email they are not able to buy our products. We are losing business. Help?

Why not simply turn off the activation email ?
In the options of the joomla user manager, there is an option where you can choose whether to activate the activation of user accounts or not.