The format of the recipient e-mail address is not valid. Valid SMTP e-mail addresses can contain only letters, numbers, hyphens, ...

{4}: The format of the recipient e-mail address is not valid. Valid SMTP e-mail addresses can contain only letters, numbers, hyphens, periods, and only one @ symbol. Troubleshooting: Verify that the SMTP address of the recipient is formatted correctly and resend the message.