Until Thunderbird added support for Exchange there was a slight hole on Linux (no FOSS mail solution with support for it) but right now I'd say everything works more or less out of the box. SPAM filtering and categorization could be a bit more automated, but in general I'd say everything is covered.

Mail server projects are a different story though. There's no simple way to create a fully fledged mail server without weeks of pain to configure spam, routing, calendars, security... there are some preconfigured images in all major cloud platforms, but nothing like `apt install mail-server` that pops out a simple config assistant in an already existing server.