You "should not" repeat delivery in basically the same way the mailman "should not" knock a second time if he's told the recipient doesn't reside at the designated address. What "should not" means in these cases is: "knock only once, and assume you're being told the truth in the absence of further evidence to the contrary". But when you clearly saw the recipient reside there yesterday, it makes sense to try to knock and catch him again tomorrow. Because, you know, maybe something went wrong, e.g. maybe the person who opened the door didn't recognize the name (or whatever). At the end of the day, the mailman's job is to deliver the mail with minimal disruption, not to play hot potato with envelopes.