I've been using Fastmail for 2 or 3 years, recently moved my XMPP and Caldav stuff over too. I would recommend them, no complaints, I've not noticed a single ou

I've been using Fastmail for 2 or 3 years, recently moved my XMPP and Caldav stuff over too. I would recommend them, no complaints, I've not noticed a single outage in that time. It was trivial to IMAP import mail from my old host. Good support for multiple authentication schemes, i.e. I have a 32 random char master password saved in my password manager, and they allow me to add any number of alternative authentications like shorter passwords that are only allowed in combination with Yubikey/Google Authenticator or one time passwords. As for "app" I just use a generic IMAP client.