Announcement email is ok now.
your plugin and/or theme is using wp cron too early, i have changed in class-fep-email-beautify.php add_action('init', array(Fep_Email_Beautify::init(), 'actions_filters')); to add_action('after_setup_theme', array(Fep_Email_Beautify::init(), 'actions_filters'));

When you update this plugin remember to change this.

If you want to find which plugin and/or theme doing so, please follow standard procedure. Disable all plugin except Front End PM and change theme to default theme. Then enable one by one and send announcement.