The error notice is rejected if it is sent with incorrect JSON/XML as determined by:
Rejections in the dashboard
You can view rejected error trends in your project overview graph.
Rejections are also displayed in your error groups list and appear as
AirbrakeNotice placeholder exceptions that provide as much information as
possible. These placeholders let you know that your Airbrake notifier library
couldn’t parse an error into the correct format.
Experimental Airbrake notifier
It’s common to see error rejections when using an experimental or unsupported
Airbrake notifiers. You can use the information provided by the
placeholder to troubleshoot your notifier.
AirbrakeNotice placeholders can be a
valuable debugging asset when developing a new Airbrake Notifier and reporting
Official Airbrake notifier
Rejections are less likely with official and widely adopted Airbrake notifiers. However, if errors sent by your Notifier are consistently getting rejected, please help improve the Airbrake notifier you are using by creating a GitHub issue for the notifier and reporting the problem to firstname.lastname@example.org.