You can use Ok emails and, in some cases, risky emails (unknown and catch-all). For email marketing, it is also recommended to filter out role emails. 

Good Emails

Ok means the email address exists, and it is safe to send emails to. MillionVerifier offers a 100% money-back guarantee on Ok emails.  

Risky Emails

You can use risky emails only if:

• they are real subscribers (not purchased list, nor collected from the internet)
• they have subscribed recently (less than two months ago)

Risk emails are:

• Unknown means that we couldn't verify the email address at the time of the verification.
• Catch all means the email server is set to accept all mail even if the email account doesn't exist. 

Bad Emails

Never use bad emails. Bad emails are:

• Invalid means the email account doesn't exist.
• Disposable means the email address is just a temporary email address.