[upofadown]

In general you should avoid doing your email through giant providers like Microsoft and Google. They just don't care. Smaller providers are more interested in ensuring that everything is actually working.

[Avamander]

Both approaches have their downsides.

The small providers can get caught in the gears of large providers or even smaller providers using idiotic RBLs (sometimes a single one that causes a permanent reject). Nobody dares block Gmail or O365 however.

But you won't have an undiagnosable spam filter. Depends on your risks.

[UberFly]

So true. Also running your own mail server can be a nightmare with bigger problems.

[nullindividual]

This is generally not practical for medium to large companies.