I'm not even elderly but I would really like an e-mail client with a stable UI. I used to like Apple Mail but it's been a buggy mess since Catalina. It doesn't even sort or search mail reliably any more. It's basically a trope at this point but a robot-rewrite-in-Rust seems inevitable at this point.

A while ago I helped an elderly relative migrate off off a copy of Eudora that they'd been using for many years. (To Thunderbird.)

Originally it was about difficulty migrating to a new laptop with a different version of Windows, but I was quite firm about it because when I realized it wasn't able to do secure connections for some reason, so the instant they took their laptop to public Wi-Fi...