With no competition for miles ....
MS can do whatever they like with Outlook, because there really is no alternative.
I think its Woody Allen than commented Science has bought us some wonderful things, but it's only when an 83-year old is left alone with a cocktail waitress and nothing happens, we realise it has failed us.
(With apologies for the of it's age misogyny)
That could be paraphrased as FOSS has bought us some wonderful things. But it's only when you try to deliver a decent Exchange-connecting Mail and Calendar client into Linux, you realise it's failed.
(The closest I have come is Thunderbird/Lightening. But they're buggy, lack features and a tad unreliable. Certainly not enterprise-grade apps).