Fastmail.com / Pobox.com I've used pobox.com since 1996. They forward inbound mail to somewhere else, and provide an outgoing SMTP server. So you can manage

Fastmail.com / Pobox.com I've used pobox.com since 1996. They forward inbound mail to somewhere else, and provide an outgoing SMTP server. So you can manage your email at Google or Apple or Microsoft or wherever, and change that whenever you like, while retaining the same public email address. Fastmail, OTOH, provides a full IMAP+SMTP service, plus CalDAV and CardDAV. So it's a complete replacement for Google/iCloud/Outlook. It's a paid service, and they are very aware that if you're actually paying, you need decent support. You can use your own domain name too. They've been around since 1999. Not email, but I can also recommend Fruux as a standalone CalDAV + CardDAV provider. It just works, at least for me. I think they've been in business since 2007.