You send an email to an invalid address. What’s the worst that can happen? It bounces, right?
Wasted Time: Your marketing efforts lead to various email address acquisition activities, but those efforts are wasted when the email addresses are invalid. Avoid wasting more time responding by eliminating invalid addresses.
Wasted Money: Email marketing services charge based on the number of emails that you send. Invalid email addresses and disposable mailboxes send both your emails and marketing dollars directly into a black hole.
Blacklist Risk: By sending emails to invalid email addresses, you run the risk of being flagged by email servers as a spammer. Once you are on a blacklist, other email servers will proactively block emails coming from you.