You will receive this message if you put a space after the email address or if the email address is not entered correctly. See the list of possible mistakes below.
Examples:
- test@gmail is missing the .com at the end
- test@gmail.com has a space AFTER .com
- test@@gmail.com has two @ signs
- test@gmail.com space@gmail.com there is not a semicolon (;) between the emails.
Updated