@shortridge 20 years ago I was running the email system at a Major Private University and one week the disks on the inbound email servers started mysteriously filling up repeatedly.
Turns out we had a 50mb limit on email size, but software at the time enforced that AFTER the message body was sent. So it would dutifully spool all the data onto disk before saying, "Sorry, rejected" at the end, at which point it would delete it.