I had Tbird running very well on my new MacBook a two months, I have it set to work perfectly with my outlook.com email account for emails, contacts and calendar. I have Tbsync and Provider for exchange add ons. In fact the whole set up was much easier on the Mac than on my old Win10 laptop. I also have BT, Gmail and iCloud email folders set up as well. As state the whole system was working perfectly, calendar events etc all synced and updated my Outlook.com account and also my iPhone. I was extremely pleased with how it was working. Problem. I switch off my Mac last night as usual. Started up this morning and opened Tbird. Latest emails were duly received from all accounts including my Outlook.com. However when I went to add a new event I noticed there were no calendars, none! Yesterday there were F1, holidays, personal. I then noticed that my address book was also gone, no contacts, nothing. Just a blank calendar and the empty Tbird default address book. No menu options for getting Outlook contacts or calendar re-set up exist. I feel rather annoyed, is putting it mildly! Fortunately the data is still there in my Outlook.com account. So not 100% angry. Despite the fact that I am downloading emails from Outlook.com, plus sending replies and new ones, something has gone missing. I must therefore assume that TBsync 4.11 or Provider for Exchange ActiveSync 4.12 has decided to go on vacation. Tbird is version 128.3.3esr (64-bit) No updates have been requested or installed for months. It just simply was working well and then decided not too! Any ideas for a fix? Or do I remove everything and start a fresh setup