3 ms·I work on Windows. I can say that Thunderbird is far better that Outlook.by Zardoz84 10y agoI work on Windows. I can say that Thunderbird is far better that Outlook.dingo_bat 10y agoI have the opposite experience.raesene9 10y agoI agree, I've tried both and whilst neither are the fastest programs in the universe, Outlook 2016 has been better than Thunderbird from a performance standpoint. Thunderbird was so slow, I went back to Outlook.