Is the CC line relevant?Yes
Did you type something accidentally? Like accidentally put the subject in the CC or BCC line?Yes! Or accidentally Paste it there?
My university uses Microsoft Office 365, which works OK enough to do the job, but is much glitchier than the other webmail programs I have used, often taking a few tries to load (particularly on mobile devices). However, the incident in this puzzle was entirely my own fault.
In an email to someone else in my lab, I accidentally typed the subject line, "More paper questions" (as in, more questions about a scientific paper I was reading) into the CC blank, most likely because I wasn't yet used to where things were in Office 365. In lieu of an actual email address, the web app tried to be helpful by attempting to parse the misplaced subject line as a person's name and looking it up in the university directory. So, right after sending I got an error message saying something along the lines of "Cannot find name 'More Questions'", with one of the colored bubbles that the program uses to represent parties to a conversation, containing the initials MQ. So somehow I had addressed that email knowing that if Mr. Questions had existed, his middle name would be "Paper".
I told you this was silly!