customers with no email

Is it possible to for the AllProWebTools system to tag any contact in our database that does not have an email address with a tag called "no email"?

You can go to Contacts -> Manage Tags to create a tag with the name that you choose.
After you have created the tag name, you can scroll to the bottom of the page where it says "Tag all contacts that have no email address" and follow the instructions in the box.