I've never known the postman to ask for identification but I believe when delivered like any post the person receiving the package has to be at the address they are delivering to, they cannot be outside the door as the postman/woman could be delivering to the wrong person.
Not normally when it is received at the address to which it has been sent but if you are going to collect it from a Post Office pick up point ( where you have had a chit from the PO about an item for you to collect) you MUST go in person with appropriate Photo ID else they will not release it ( as several customers found out to their cost recently when they tried to collect items that were not addresses to them ; they were furious but it states on the card to collect in person and bring photo id with you )!!
"...do the receiver have to show ID to the post man"
No, because it wouldn't be practical to insist on one - the chances of a named recipient being there at the exact time the delivery is made are slim at best. What you get is a copy of the signature of the person who accepted the letter or package.
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