Filter wp_mail based on content type
Note that the wp_mail filter runs before the wp_mail_content_type filter. If you’re using the PHP Mailer then you can try (untested): add_action( ‘phpmailer_init’, function( $phpmailer ) { if( ‘text/plain’ === $phpmailer->ContentType ) { $phpmailer->Body = ‘Filtered text here’; // <– Message override } });