I have installed the exception notifications gem and I am currently using sendgrid as part of my app email sign up/login process.
Below is my github gist which i added the config code in my production.rb but not sure why I am not receiving any email.
I am not sure what went wrong in your code. Try following code this is working one in mine.
On command prompt :
config/environment.rb:
config/initializers/exception_notification.rb:
Gemfile:
config/environments/production.rb: