adding non-user customers to acymailing

Our site is set for no user registration, is it possible to add the customer's email addresses to acymailing when they aren't users?

You can use the acymailing import feature to import the email of the user in acymailing:
table => jos_hikashop_user
email field => user_email

That will import all the emails in acymailing.
Then, with the enterprise version of acymailing, you can also automate that using filters so that the users are added all the time.