It’s not impossible, been running my own email server for about 10 years and I inbox pretty much everywhere. I even emailed my work address and straight to inbox. I do have the full SPF, DKIM and DMARC stuff set up, for which I get notices from several email provides of failed spoof attempts.
Takes a while and effort to gain that reputation, but it’s doable. And OVH’s IPs don’t exactly have a great reputation either. Once you’re delisted from most spam databases / old spam reputation is expired, it’s not that bad.
Although I do agree it’s possibly one of the hardest services to self host. The software to run email servers is ancient and weird, and takes a lot to set up right. If you get it wrong you relay spam and start over, it’s rough.
It’s still not ideal but you can at least set a charge limit and set it really low like 50% which is about where those batteries degrade the least.
But yeah using a lithium ion battery as a capacitor ain’t great. BMS is just gonna charge it some, let it drain, charge it some, let it drain, repeat over and over again. There’s a reason store phones tend to become spicy pillows so much after a while of being on display always on always running some animation.
This is already what happens when you leave it plugged in to charge overnight, except it uses very little power so the battery only gets topped off a handful of times.
The heat caused by the busy CPU would also be a rather big problem for the battery.