In terms of email marketing this is a process of checking email address to see if it is dead or we can keep it in mass email list. When I say dead I mean that messages we send to a dead address bounces back with messages like this:
- Hard bounce. It happens when during email check server says “User unknown” or gives you a similar message. This is a permanent problem. Email is invalid. Email is dead or never existed.
- Soft bounce. Server says “mailbox is full” or all kind of a temporary problems. You got a chance to email it later when it is back to normal. Decide whether to keep it or move into a list to check again later.
Remember, when you send mass mail the bounces you get the higher chances of getting blacklisted by SMTP server provider or mail service like mailchimp, iContact etc.