To use your own email server in Run Free Project:
In the Integrations section of Store Settings, choose the email section on the left.
Toggle on Use Your Mail Server.
Enter your SMTP server, port, Username and Password.
Hit Save in the upper right.
For Gmail: Here is the link for generating an app username and password: https://myaccount.google.com/apppasswords
NOTE: In order to generate an app password you must have 2-factor enabled on your Google account. https://support.google.com/accounts/answer/185839?sjid=13471358991141727918-NA