Not looking for a server as I use fastmail currently but a client would be nice. I am currently using spark on iOS and Mac OS and just fastmail website on my Linux desktop. I’m realizing spark is nothing special and would rather not renew my subscription.
An email client isn’t exactly something that’s self hosted. But Apple Mail works perfectly fine on iOS and Mac OS. Fastmail has push support too.
You can host a webmail like roundcube or similar. I don’t know if they can be turned into PWAs with phone notifications though.