I seems to have everything te same as your test, the 1 exception is the notification. I was sending 2, one for the failover to cellular data and a 2nd to let them know it was back to the main. I tried it with 1 notification set to all and i do not recieve a notification of it switching to cellular. The log shows email sending to user "firstname.lastname@example.org" failed.
Testing the notification works correctly, So it can send.
Is there a log with more info?
I also tried to use SMS. those never send and I can't generate a successful test either. I may go to Verizon and have them test the sim in a phone to verify it is capable.
As I am replying, I am wondering if Verizon is blocking the ability to send emails. I am using port 587, I will see what other options I have and test those on the cell connection. My thought is when I tested sending email I was on a wired connection. If that's the case. My other guess is the service does not have sms