One of our hosting companies that we have a reseller account on has disabled PHP Mail function for security reasons. This causes the WordPress sites that use Contact Form 7 (with Really Simple CAPTCHA) to fail with,
“Failed to send your message. Please try later or contact administrator by other way.”
To fix this you need to enable the WP-Mail-SMTP plugin. To install this download the plugin and upload to your site as normal and then activate this on a per-site basis (not Network activate).
You will now have new options in the Settings -> Email on your site dashboard of which the most important is “Send all WordPress emails via SMTP.” (checked by default).
Set these parameters as per your hosting provider recommendation though you usually can just specify one of your own email addresses on your domain as the From Email and set it to localhost and no authentication and it should work.
It is usually only when the from email domain is not a local domain on that server that you will have problems and need to authenticate your connection or if the SMTP server is not “localhost”.
If you have it right then you will get the message “Your message was sent successfully. Thanks.”