> What to do with pile of letters?

What to do with pile of letters?

Posted at: 2014-09-26 
Write 'Gone Away' in large letters and stuff them into the nearest post office pillar box.

Write "NOT AT THIS ADDRESS" And pop them to the post box/office

Write on each envelope "Return to sender, not known at this address" and put them in the post box.

When letters for previous tenants have been delivered to our flat my flatmates have stuff these in a draw. They've been doing this since before I moved in so now we must have 60+ letters of various ages for various people.

Now I'm wondering what to do about them, many look like bank statements and others are 'private and confidential', so throwing them out doesn't seem right. Plus the landlord doesnt know who they are, which makes me wonder how long ago these people lived here, but then he can never remember who lives here now