You should try to use a Restricted Gmail SMTP server.
Google provides three different SMTP settings in which you can send email messages from a printer, scanner or application (PLC).
SMTP relay service – used to send mail from your organization by authenticating with the IP address(s). You can send messages to anyone inside or outside of your domain. Gmail SMTP server – requires authentication with your Gmail/Google Apps account and password. Messages can be sent to anyone inside or outside of your domain. Restricted Gmail SMTP server – does not require authentication, and you will be restricted to send messages to Gmail or Google Apps users only.