YSK You should always include your own address on parcels and letters containing gifts

I read about a case recently in The Guardian where someone believed they lost a £50 gift card in the post and didn't include a return address on the envelope so it couldn't be traced.

If a return address isn't visible on the outside of a parcel, the mail dept are allowed to open it to look for one inside if they cannot deliver it to the intended recipient. Mail that cannot be traced back to anyone or sent on to anyone could end up at a "dead mail" office.

In some places, such as Australia, the postal service won't handle packages unless you do this.

TL;DR: Don't forget to use your common sense.