@rsiegel maybe this can help to resolve this issue
I have done some testing today with different hardware and software setups and i have found that device trigger notifications do no recycle PINS USED for it or delete them on server side for some reason.
Case 1 Works:
You setup new device named Device1 mqtt adds channels, you go to trigger and setup notification for some channel/pin to send Email or SMS or both on some event. Its works
Case 2 Does not work:
You go to that same Device1, delete pin/dashboard that was using trigger from previous Case delete trigger for it, after that mqtt adds same pin/dashboard from previous Case. When you now add trigger for that pin which was temporarely deleted, the trigger notification does not work
So evereytime you want to edit trigger, you need edit code for the esp and change pin on which data are sent then add new trigger. Not very practical 
Case tests were made using mqttesp lib and stand-alone esp module reading temperature values from 3 different sensors and writing valuse of them to 3 different cayenne pins.