The Check-up section allows you to perform one last check-up before sending the email message.
This section allows you to check a number of features pertaining to the settings of your email.
In addition, the Check-up section allows you to analyze if the HTML code has any errors (HTML tab), if your email has any spam words (Spam check), and how your email is mobile-friendly (Mobile).
Once you analyze the Check-up, you can either go back and modify your email or continue to send the email.