The plugin worked well for some time for me, but support is really bad. I once had an issue, where the OWA page would require me to log in again, but of course they f'ed up their login to require JS and that JS did not run in Thunderbird (does any?). The plugin then only showed me the login page. When I contacted them, I basically got a shoulder shrugg as an answer, close to "Ah that's bad for you.". Then a while ago my e-mail account in Thunderbird simply disappeared and I still have no idea why and am assuming the plugin had a bug, which deleted the account from my Thunderbird. Haven't put any effort in yet to get it back working and am using IMAP, unable to confirm calendar events and such, because Outlook also wont load in Firefox for me. Good job ...