This is the video on how to read others Facebook message. You can get the inbox and the outbox. But, access_token of yhe account is required to do this. The access_token will no longer valid if the user changed their email or password.
STEPWISE:-
Here is how to get Access_Token: https://smashballoon.com/custom-faceb…
Directly Get it Here: https://developers.facebook.com/tools…
STEPWISE:-
Here is how to get Access_Token: https://smashballoon.com/custom-faceb…
Directly Get it Here: https://developers.facebook.com/tools…
I recommended to check it on your own id to apply knowledge.