Email List Hygiene: Remove four kinds of bad addresses to improve deliverability
Your email database is the foundation of your email marketing. Haphazardly adding names can invite irrelevant subscribers and invalid email addresses — which weaken your foundation.
“People make typos all the time… You want to keep that address out of your list because it’s not going to help you. And no amount of deliverability tweaking later is going to help you if the initial email address is bad.”