We use Microsoft Exchange for our email, and we probably always will. We host Exchange on our own server and have webmail. This was the reason I was tied to Evolution for so long; Evolution was the only Linux client which supported Exchange Web Services directly in the client. Thankfully, Davmail takes care of the conversion for any email client, and I was able to switch to Thunderbird. Unfortunately, no such software exists for phone operating systems like Android.
I don't think any free software app on Android supports Exchange Web Services, so I use webmail in the browser (I really don't like Outlook). This is a feature which would set Thunderbird on mobile (K-9 Mail) apart from other email clients.
I'd love to use K-9 Mail!