Using wp super cache can cause problems if not setup correctly.
?
?There were also some new rules released for mod_security alongside the latest release of WordPress which appear to have tightened many hosts email sending restrictions. Make sure your From: email is a valid email address – preferably one on your website domain.
This is just one of a host of issues that can stop or delay emails on both the sending and receiving ends. It depends entirely on your local Server & WordPress configuration. You will need to investigate this issue for your particular local configuration.
See Contact Form 7 Email Issues. Most people that work through this information appear to be able to resolve their email sending & receiving issues.