Interesting: Basecamp are launching a new email service called Hey: https://hey.com
My educated guess would be that they won't bother with PGP support at all.
However, at this point, anything that gets people out of GMail is a net win in my book. No one company should hoard that much unencrypted personal communication.
Ah yes, all unencrypted, of course: https://twitter.com/dhh/status/1225520993973633024
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!