Check out how you can verify an email id from here. It's common scenario that we receive the delivery failed notification hours after sending an email.

However, there is no denying that it is a major data breach. And, it is important to check if your email ID and password have been compromised or not.

How to Check for a Valid Gmail ID. When sending marketing, promotion or business-to-business emails, you want to confirm that the address is legitimate and clients will receive your messages.