If you’re looking for more tinkering on the music around the house front, Lyrion music server + squeezelite players can be a very fun endeavor. I think it gets a little sketchy if you’re favoring automation and casting, but as a network of players that will utilize a wide swath of hardware, it shines. I had a bunch of pi4s laying around and eventually repurposed them all into a multiroom audio gang.

Startmail (from the Startpage folks) has been fine for me. You pay for it, you can put your domain on it, you can do alias addresses, works with any IMAP client since it’s just IMAP ran by a (so far) competent company. Their web ui is fine, but ive only used it for initial setup. Besides Thunderbird on mobile I use Snappymail within Nextcloud and this works just fine as well. All I can say is it does what it says on the tin.