Updated bulk-email service to use mailgun settings
Updated bulk-email service to use mailgun settings

refs #10318

bitjson/Ghost,e10/Ghost,janvt/Ghost,ErisDS/Ghost,JohnONolan/Ghost,TryGhost/Ghost,ErisDS/Ghost,TryGhost/Ghost,JohnONolan/Ghost,janvt/Ghost,TryGhost/Ghost,ErisDS/Ghost,bitjson/Ghost,JohnONolan/Ghost,e10/Ghost