It's always recommended to check what your emails actually look like before sending them to hundreds of contacts.
When editing an email step in a campaign, you can click on the Send Preview button to send a preview email:
You can choose who you want to send the email to and what sending address to use.
You can also choose to fill the template variables in your email with values from the last created contact. This is useful to test if your variables and fallbacks are correctly set up.