Email address validation is the process of checking if an email address is correct. There are a few parts to email address validation. You can use Real Email to do this checking.
Email server exists at the domain, the part after the @
The account exists for the user
Email address validation can be important for the following reasons.
Improving email deliverability
Making sure your delivered emails don't get classified as spam
Ensuring compliance with email sending services
Saving budget on sent emails
Blocking spam users who are using a fake email address