Oh, that wasn't the impression I got from the OP. It sounded like a personal project, but I suppose some people can't change. From an IT perspective, my employer doesn't care what OS I use as long as the job gets done. I can use whatever I want. At home I run an ESXi server, so if I want an OS to use, I spin one up.
Oh. Misread your post as general advice, which doesn't work. But, yeah, for most private persons it works
Outside of outlook, is there anything you can't get from there through open source?
If you refer to the subscription thing and Office, here's an example: If you write, say novels, you want to get published. At some point, that means to submit your manuscript. To multiple people, one at a time (agent, editor, proof-reader, translator etc.).
The standard for that is, still, Word. It goes back and forth, with the comments and change tracking turned on. The initial submission might still work with a .doc/x file put out by something other than Word, but after a bit of back and forth with the comments and change tracking, it's still more likely to work with Word directly, instead with, say, LibreOffice (which is, AFAIK, the only viable alternative that has all the functions needed).
Never mind that no one really wants to work with Word (aside a few freaks), and that there are better alternatives, and that, for instance, a simple plain text (with a bit of simple mark-up like MarkDown) would allow anything you would need for the process much simpler, safer and stabler. Or that the final steps close to printing involve completely different software and formats.
It's just that Word, and its format, is so embedded in the publishing process that a decision on a different standard is nigh impossible.
There is hope that electronic publishing (both self publishing or with a publisher) may change things, given that Word still revolves around pages and letter/A4 sized paper, which you positively do not need at all for electronic e-books.
