Secret Mail Puzzle

The Puzzle:

Secret Mail
You want to send a secret message to your friend Alex in the mail.

But Sam, who you don't trust, has access to all your mail.

So you put your message in a box with a lock.

But you are not allowed to send a key!

How can you get your message through securely?



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-\./^\./-


Do you have the answer? Check against our solution!