Every AIMStorefront will need to connect to an email account so that it can send receipts, lost passwords, contact us information, new order notifications, rental notifications, etc. Basically, anytime your store should send and email, it needs to connect to your email provider and send that email using an email address you own.
This can often be the trickiest part of setting up your store. Since AIMStorefront does not use email any differently than AspDotNetStorefront, you can follow our setup instructions here: https://help.aspdotnetstorefront.com/1000/email_setup.htm
If you are specifically using Gmail or Gsuite as your email provider, please follow our instructions on this page