WP Mail Array

Based on the error, it looks like there’s a “wp_mail” filter defined on your site that is returning null. The odd thing is, the core wp_mail() function that this replaces does the exact same thing. Can you check whether the same warning appears when the plugin is disabled?

I can add an is_array() check to make the function more robust, but it seems strange, since the core function doesn’t do that, so the plugin be deviating slightly in behavior.