FWIW. After I bought my current house there were phone calls for abut 18 months for the previous owner, chasing a debt. I didn't have the new address of the man, and only knew where the woman worked. They were divorced anyway.

Out of prudence I was in the habit of going round from the back when cold callers knocked on the front door. Locking the back door in case it was bailiffs/burglars nipping in the back while I dealt with - whatever.

The reason: if you open the door to a bailiff they could, and they ain't too polite by nature, get a foot in the door and once "in" they could claim things and return any time claiming they have once been invited. Sorting that out in retrospect was not my idea of a game.

That all seemed a bit over-the-top but this was a game I was not going to loose. And it gave me the advantage with cold callers. And mind games are entertaining - if you don't loose.

As for the letter in the OP, doing "nothing more than binning the letter" is not good advice! IMNSHO