It's one of the great mysteries of 2013: What's inside your Facebook account's "other" folder?

It's a little-known bit of social-media savvy that on Facebook, there are two folders for private messages, your inbox, and the "secret" other folder.

The latter is supposed to filter out spam, by diverting messages from people who aren't "friends" or "mutual friends." But after New York Times tech writer David Pogue wrote about the other folder last week, surprised readers began looking inside. What many found wasn't spam at all – but missed career opportunities, messages from long-lost friends, notifications of prize-winnings and invitations.

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"Whoa! There's tons of important messages in here," commented one reader. "Former students of mine were trying to reach out to me. I can't believe Facebook doesn't notify you in any way about these."

It's true: Facebook doesn't send push notifications about messages that land in the other folder, and the folder isn't accessible on the Facebook app for mobile phones or tablets.

In Pogue's latest roundup of reader comments, grumblings and jokes emerge:

"Just looked at my 'Other' messages and found one about a job opening – in 2011. Think it's been filled?"

"Shoot, I just discovered I had won a contest for Knicks tickets, but the message was in that 'Other' folder. It was from 2011. Grrrr!"

For some, the tip-off came with time to make amends. ("Now I have to apologize to several past acquaintances and let them know I haven't been blowing them off!")

For others, it was time to make merry. ("Just found a message from a long-lost friend in my 'Other' folder. I'd been trying to find her for more than a decade with no success. David Pogue, when she and I finally reunite, our first glass will be raised to you!")

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Here's how to check your other folder: Open Facebook in a Web browser, then in the private-messaging section, click on the "other" link to the left of the "send a new message" function.

But how did so many people miss the folder in the first place? For one thing, the word "other" itself is pretty easy to overlook. Should Facebook consider renaming the folder to something more eye-catching? A sonnet by Dante Gabriel Rossetti offers some poetic suggestions: "Look in my face; my name is Might-have-been; I am also called No-more, Too-late, Farewell."

Now that you've checked your other folder, tell us: What are some of the long-lost messages you've discovered in there?