To add to others' comments about mail-rooms and internal posts, a memo would commonly also have a header section with a list of intended recipients and CC (lite

To add to others' comments about mail-rooms and internal posts, a memo would commonly also have a header section with a list of intended recipients and CC (literally, Carbon Copy), plus depending on organisation, an information security classification meaning sometimes they would be distributed via envelope, or require signing receipt for. Envelopes could be sealed in any number of ways, the most common I've seen is masking tape with a signature across it. Needless to say, the mail-room were privy to a lot of information should they care for it. Edit: Working where both emails and physical memos were used: Drafting a physical memo elicited a very different state of mind from banging out an email. Printing it out, proof reading on paper, there was a lot more care via reflection knowing this would be in someone's hand and they'd likely be looking at it on their desk, giving full attention, making notes with pen over it, rather than simply a message displayed on a screen while multiple other tasks pop up from other incoming mails or calendar reminders or IM chats. Slower, but a level of preciseness and everything needing to be just right, all the way down to how many spaces after a period vs a colon.