Your Website Bounced A Message To ...

In May 2017 a new email sending service was put in place to send all messages generated by the website.  One of the many benefits of this service is that it can detect if there was a problem delivering the message to one (or more) of the recipients, and if so, send an alert back to the site which triggered the message in the first place.
Accordingly, each site now listens for these alerts and when it receives one it sends an email with several details about the original message, the failed recipient, and any actions that the site may have taken to try to prevent future issues.
By default, the site will send the notification of a bounced message to all non-expired Global Administrators setup at the time.  This should only be a small handful of people anyway, however, to specify a specific person to receive the notifications of bounced messaged you can go to System Administration -> Email Administration -> Email Settings and set the bounce notification address there.
Please ensure that the person(s) receiving the bounce notifications take the time to read the contents of the message as there may be additional action required in order to fix the problem.  Usually at the bottom of the bounce notification email there will be specific details about what action(s) were taken or if there are things that should be done it may provide suggestions.
The biggest cause of bounced messages will be from folks who subscribe to receive email notifications from the site and mis-type their own email address.  In these cases, any emails sent from the site will probably "hard bounce" for that recipient.  If that happens, the website should be able to automatically remove that email address from the list of subscriptions to prevent further bounces.  It is impossible to notify the recipient that they've been unsubscribed because they entered their wrong email address - so if the person(s) receiving the bounce notifications recognize the failed email address, and know what the correct one should be, it would be courtesy to email that person and let them know they need to re-subscribe with the proper email address.
Another cause of a bounced message might be from emails sent to the email address associated with a login to the website.  This could be a big problem for that person since they probably would not have received their password to login, and certainly won't receive any forgotten password requests.  If the login is associated with a game official's login, then that means they won't be receiving notifications related to their assignments or other potentially important details.  The bounce notification email will have a large red box warning when this happens and the only fix which can be made is that a person with access to the System Administration area update the login in the Manage Users area with the correct email address.