Same issue here, seems like O365 connections got borked somehow?
Arch Linux running mailspring 1.10 - anybody find any workarounds aside from downgrading back to 1.9 (which won’t open with latest package upgrades on arch unless use --no-sandbox)?
Also - anybody try re-adding the account to see if any different vs reconnecting an existing one that was there pre-upgrade?
(Also duplicate under sync issues - 400: Bad Request when using Office 365 authentication )