With numerous new themes and new versions of the wordpress, when you try to publish some post or page or try to send email or try to use contact form, you might get following error:
Fatal error: Call to undefined method PHPMailer::getCustomHeaders()
This error normally occurs if you are using incompatible wordpress and theme and plugin versions. The best course of action is to update your wordpress, your theme, and all the plugin and make sure that contact form 7 plugin isn't complaining about the wordpress version.
If you cannot upgrade your versions or if the error is occuring even after the upgrade, then you can do the following workaround:
Make the following change in your mail.php file in the directory wordpress/wp-content/plugins/contact-form-7/includes
Go to the line 171 and change:
add_action( ‘phpmailer_init’, ‘wpcf7_phpmailer_init’ );
//add_action( ‘phpmailer_init’, ‘wpcf7_phpmailer_init’ );
Hope that helps.