Priscila, isn't the WP Mail SMTP plugin just for sending email? Not sure how to configure it to receive email using Contact Form 7.
Yes, it is. It also helps authenticate and allow the server to send out emails to outside servers. Even though you have Contact Form 7 for the forms, the WP Mail SMTP plugin helps sends it out for the servers that requires authentication. The emails generated by the Contact Form 7 forms will automatically send out once you have this plugin installed, activated and added information in the Settings >> Email information.
If this does not fix you problem, please specify details, error messages, or link to the form.