On Wednesday we had an unrelated email issue with our host, and they made some changes which included removing our domain,
This had some far-reaching (and difficult to diagnose) implications, and we didn't actually notice that mails weren't being delivered at all until Thursday. I spent Thursday mistakenly trying to figure out what was wrong with our email cronjobs, but on Friday I finally found the real problem and fixed it.
The issue now is that there's a lot of email missing from the last two days. I need to find those missing messages if at all possible, but unfortunately googling for "courier where do failed emails go" results in a bunch of news stories about meatspace shipments. I've checked inside
/var/mail but the files within are empty - I guess cPanel or Courier does things I don't expect with email.
My question is: Where would the undeliverable mails from that period go? Is there any possibility they still exist somewhere and I can recover them?