Sounds about right. Yes, I've been doing it for decades now and besides telling you who's selling email lists, it makes filtering much easier. Filtering by To: is pretty low effort compared to Bayesian spam filters etc. They get tossed in a Sieve filter as soon as they become a problem, and I'll send a bitch letter to the leaker with another random email address to see how dedicated they are to screwing me.

How is this possible for any normal person with a work provided 365 account?