Unified cloud based email calendar contacts tasks platform

I don't know if something like this exist (other than Gmail, Office 365) but I am looking for a cloud platform that can do this. Basically its cloud based Thunderbird.
-imap email for multiple inboxes/accounts
-caldav and google calendar
-carddav address book
Paying subscription is fine. Currently using Thunderbird and that is the only app I use that requires a local copy/install.
Appreciate feedback if you know of any.

There are a lot of O365/Gmail alternatives out there, but not all will have tasks. Zoho Mail is likely the best alternative with the most features.