function wpcf7_before_send_mail_function( $contact_form, $abort, $submission ) {
$your_name = $submission->get_posted_data('your-field-name');
// do something
return $contact_form;
}
add_filter( 'wpcf7_before_send_mail', 'wpcf7_before_send_mail_function', 10, 3 );