There are several methods to verify email sources effectively:
Double Opt-In: This involves sending a confirmation email to the user after they sign up. Only after the user confirms, their email is added to your list. Email Verification Tools: Using third-party services like ZeroBounce, NeverBounce, or BriteVerify to check the validity of email addresses in your list. Regular List Cleaning: Periodically removing inactive or unengaged subscribers from your list. Domain Validation: Verifying the domain of the email address to ensure it is valid and active.