Here are some forms of inter-office communication one might encounter in real life or fiction:
Junior high: 5th-period student assistant
Star Trek: communicators
Ministry of Magic: paper airplanes
Star Wars: mouse droid
The mouse droid wasn't just for carrying notes around spacecraft though: according to Wookiepedia, it could also be used for sanitation, security (mostly as an alert system, I'm guessing), and navigating troops through Imperial ships to wherever they were needed. Direct quote from Wookiepedia: "Their use was only limited by their owner's creativity."
And here I thought they were just there to feed the cat droids. :o)
You can see mouse droids in Episodes III, IV, V, and VI.
Lego Mouse Droid: