Stolen from @vmstan
More analysis from @wiredfire:
It’s nothing to do with [difficulties in using multiple platforms]. It’s to do with the massive backlash they got on Fedi for their CEO being all Trumpy and somewhat horrible right wing. So they’ve run away because they were made to feel unwelcome on account of us not letting their BS fly.
Original screenshot is of the bio of https://mastodon.social/@protonprivacy and wasn’t a post (that confused me for a sec).
I found this site useful. The list of alternatives is very large.
From my looking around at other info and advice, I’d say that Posteo is the best one if you don’t have custom domains; and that mailbox.org or possibly Tuta mail is best if do need a custom domain. Tuta is probably best if you need it to be free.
Another solid option not on that list is fastmail.fm (which is Australian).