Postfix - outgoing mail history?

Is there a way to see if an email was sent, or attempted to be sent, through Postfix? We have an app that sends email alerts through a Debian-based Postfix server and apparently something rather important didn't make it out on 1/6. I've been asked to see if it ever made it to the mail server or not and I'm not coming up with anything since it's not currently in the queue.