Another reason is that many email service providers use a variety of tools to reduce email spam. These tools often try to detect that an email is originating from the location it claims to be originating from.
Please have a look at this post to solve the mailing issue at your website: http://www.wpbeginner.com/wp-tutorials/how-to-fix-wordpress-not-sending-email-issue/
To start using Mailing, you will need mailing plugin.
There are a lot of 3rd party plugins that could work with EngineThemes:
Please try to see which plugin would work best for you.
Also please make sure that you have enabled the email confirmation option in Engine Settings.