If you're the SENDER :

Better affix nice stamps on the cover you send to your Helper : thus, your Helper will be more likely to do the same for your Recipient !

Don't enclose things of value in your covers. The website can't be responsible for loss...

Don't imagine that your letter will reach your Recipient very fast if your Helper lives on the other side of the planet ! Sometimes, it takes quite a long time...

You can find here a model of letter to precise some things to your Helper.

If you're the HELPER :

Don't add your postal address on (or behind) the cover you send to the Recipient :
Helpers are the ones who make it magic for the Recipients : things have to remain mysterious !

If you're the RECIPIENT :

Your turn to become a Sender or a Helper !