The only way without 3rd party tools is to do the direct email to carrier route. However, I've seen it be an OK solution sometimes.
(e.g. firstname.lastname@example.org for verizon)
I use to just do the email to carrier route but during an outage where several alerts were sent the carrier would either block or slow down the delivery of those messages.
I eventually moved to a 3rd party solution and never had any issues.