Undeliverable/bounce back messages

Matrix does not send any sort of undeliverable or bounce back notification when a user sends an email to an incorrect or invalid email address.

Since you are not technically emailing from your own account, but rather sending the message off of the Matrix email server (which is spoofed with your address), there cannot be any sort of undeliverable/bounce back email to notify you that there was a problem. 

Bounced back notifications only go to the point of origin (Matrix email server) and not the spoofed address.