[Outllook.com] Mail-service integration in diverse .* management systems

Good morning

I am not using Microsoft and do not work in an environment that would
benefit from “relation management” - or “document management” systems in
the wider sense of the expressions.

Now I tend to inform people who are unaware that their public mail is
directed via outlook and most probably passes servers on the other side
of the ocean.

The regularity with which I receive mail from public services in France
(i.e. from around the corner) that *do* have their own mail-servers but
direct their collaborators' mail via outlook.com, becomes overwhelming.
It is more the rule than the exception, even for organisms that claim to
be “at the edge of technology deveopment”.

My question is however simple: Is there an *obvious advantage* to use
outlook.com instead of your own mail-server, while the systems in question
allow the integration of just any mail-service under the sky?

TY

Michael