There are some situations while developing the website for client you might face issues related to email failures through WordPress.
In that case it becomes very handy if you have errors log to let you know the error/bugs/issues you are facing with emails settings.
For this Christian Zöller has posted a plugin WP Mail Logging which keeps the emails errors logs for you so that you can debug the issue also have records of the forms submission if it does not reach to you in emails notification.
Below is the video demonstration for above mentioned points.
Version at the time of demonstration:
1) WordPress: 4.9.8
2) Localserver: XAMPP Control Panel v3.2.2
3) Contact Form 7 v5.0.3
4) WP Mail Logging v1.8.4