So, I'm working for $client, and I needed to send a presentation to my $boss so that he can push it up on the webinar system for a brownbag I'm presenting today at lunchtime. He wanted both the powerpoint (ugh) slides (converted from nice nifty Keynote), and a backup PDF in case things broke.
When I printed the PDF from powerpoint, it came out as a whopping 22 Megabytes. Ouch. However, I didn't notice this, and simply attached the message in Thunderbird (another ugh, but that's another story), and pressed "send". My message was rejected during the send (and also took a while), so I found a way to reprint the PDF from the original Keynote, and it came out to 252K, so I happily sent that along instead.
But now for the "WTF" moment. I get a message about 20 seconds later from "the mail administrator" (not a human), advising me that "the attached message is too large to deliver". Yes. Follow the logic. The attached message was too large to deliver, so it delivered it to me in its entirety.
If only I had faked the "from" on the original message, the bounce would have been "delivered" to the desired recipient instead!