The e-mail address is invalid or does not exist in the recipient e-mail system. This code may be caused by an invalid non-SMTP ...

{4}: The e-mail address is invalid or does not exist in the recipient e-mail system. This code may be caused by an invalid non-SMTP address of the recipient. Troubleshooting: Verify that the non-SMTP address of the recipient is formatted correctly and resend the message.