Ask HN: Email/calendar for startup/small company?

What kind of email/calendar/collaboration solution would you suggest to evaluate for a start-up of 3 people (more planned)?

Context: I'm about to start a company with a B2B focus. We know we'll have to collaborate with people from other companies (including larger enterprises), so the tooling needs good support for Office documents (plus easy collaborative editing). So we'll probably need to go for Microsoft's 365 solution for that.

For email/calendar I naively had hoped to stay away from Microsoft's SaaS offering, but the price difference compared to the "apps-only" package is very small. Any other paid email/calendar solution is probably more expensive.

Any suggestions for other solutions/combination of solutions to consider?

Currently on my list: - Google Workspace - Fastmail (email + calendar) - Hey.com (but what to use for shared calendars?)