How to stimulate message sendingStatus: failed

Hello, I am aware that there’s sendingStatus property with possible value - failed for messages. May I know how can I stimulate a message sending that will return me failed status? I would like to add handling for this scenario but couldn’t test it out .

Also, what are the possible conditions that will actually return us a failed status?

Thank you!

Currently Im able to identify that SPAM message will be marked as failed. May I know what other conditions will mark message as failed?