I sent a trade to azzy. Then I got two pms:
Trade Update
You are being notified because the status of one of your trades with azzy has changed.
Trade Cancelled
You are being notified because your trad with azzy has been cancelled.
Apart from the spelling mistake... Apparently azzy thought they could only cancel the trade because nothing happened when they accepted. Now the funny thing is, I followed the link to the supposedly cancelled trade and was able to confirm it. And it's listed as a completed trade in my history now.
Azzy doesn't seem to have received the items though.