[Hikikomori]

Company I worked for switched from Lotus Notes to Office365 7-8 years ago. The email client was decent but weird, which was a lot better than Microsofts. And the chat client actually worked, unlike Lync for business (chat on multiple devices was completely broken).

Main reason for switching was that it was going to pay for itself, as Notes was expensive. But we also had hundreds of applications in Notes with no replacement plan or budget to do so, so they barely got rid of any licenses.