SurveyMonkey sends out a simple welcome email with a central CTA to "Start now".
When a survey is created but not sent, SurveyMonky sends a follow-up email to remind you to send the survey. This is a great way to people to come back into the app and eventually upgrade to a paid plan. The more chances people have to get back into the app, the higher the app usage, the more likely they are to upgrades. The name of the game is to get people back into your app.