Is it possible to suggest a user adds us to their address book?

Hello, Yesterday I subscribed to a companies list. As part of the sign-up, there was a pop up asking me if I wanted their contact details added to my address book. This is something I usually suggest to my contacts to try to avoid my emails from Keap (IS) going into SPAM folders. However, I found the automated request from this other companies subscription process very easy. Does anyone know how to set it up?

This wouldn’t be anything native to IS/Keap. Generally to use features like this you’d need to have an optin page on your own website (that is integrated with IS/Keap) and provide the mechanism for the popup via a plugin or other code based solution.