I have not explored what Gandi offers, but I can tell you Fastmail has a very user-friendly & intuitive interface for email, calendar, contact management, etc... a la Gmail many years ago. If not better. The $30/year includes all these services. And, I would think, since email is Fastmails bread and butter, it gets all the attention, as opposed to being an add-on/additional item that may not be top priority for a company.

And, to be clear, I have no stake in Fastmail, nor do I work for them, I am just enamored with their product. I wish I would have made the switch years ago.

Calendar and address book (with CalDAV and CardDAV) is another thing.