Lexmark CX730
From the control panel, navigate to Settings > E‑mail > E‑mail Setup > Disable “SMTP Server not set up” error > On.
To prevent the error from happening again, do one or more of the following:
Here are steps on how to set up Gmail SMTP server for Lexmark 2016 up to the latest devices.
Here are basic troubleshooting steps if you cannot set up etherFAX in your printer.