When a new user account is created, or any of the following changes are made to an existing user account, an email is sent to the user:
The system indicates an email delivery failure when an email is returned to the system as undelivered.
A red flag at the top of a page indicates issues with the email delivery.
To view and fix errors, follow these steps:
Click the flag to reveal a list, and select Email Delivery Failures to go to Setup >Users.
Alternatively, from Setup >Users, you can find users with email failures. Select Only Users With Email Failures under Toggle secondary filters.