Yes, you can add them to the contact list inside the email account that you are using with that contact.
Using a contact list on your smartphone, such as a Google contact list would not be effective (outside of Google's Gmail).
@sandyf wrote:
@maverick1 wrote:
By placing a sender's email address into your email account, it will prevent such emails from going to spam.
Did you mean into the contact list? Thanks for that tip.