Detecting mail in the mailbox, too far for WIFI
I have two suggestions that seem, to me, to be very simple:

Walk to the mailbox to check for mail. Very few people get enough exercise, so a few extra laps will, most likely, be beneficial. Of course, your dad may not get around very well these days, so that may be very impractical, which leads me to...

Check once, later in the day, after the latest time known for the mailman to stop by. Unless there's some critical reason to get the mail out of the box the moment it arrives, just check at 5pm (or whatever time is convenient).


I'm all in support of high tech and cool gadgets, but sometimes we get so focused on the gadget that we miss the point...
If there is a desire to tackle this simply because it's a challenge, I get that too. Try looking into a &quot;cantenna&quot;. It's a way of extending WiFi signal range, sometimes quite significantly (into the mile+ range, if memory serves). A cantenna on the mailbox and one on the house and Bob's your uncle!