Thanks, Fredonline and sorry not to be clear.
At the moment I am very happy with Fastmail and like the calendar very much and use it. It occurred that some time in the future I might want to/have to move away from Fastmail. I *think* there are some good email hosts that don't have calendars. It's possible I'm wrong here.
If I had to use one of those, then how do I link it with a calendar?
(The more I think about it the more I realise the question is dumb!)
Yes, Gandi would suit well if ever I came away from .Fastmail.