Many Linux users can use Evolution for for e-mail and calendar. If that works, it is a very good solution.
2018-10-16 The plugin/add-on that was previously recommended, EWS Exchange Provider, doesn't work with the newest version of Thunderbird (version 60).
An alternative is to use TbSync instead. Please note that it has not been throughly tested at UiO, and that the developer reports some known issues: For example, "sending or responding to meeting invitations is not fully working". We recommend that you reply to meetings in OWA.