Microsoft: Outlook email sending issues for users with lots of foldersMicrosoft has acknowledged a new issue affecting Outlook for Microsoft 365 users and causing email-sending problems for those with too many nested folders. [...]
Source: Microsoft: Outlook email sending issues for users with lots of folders (https://www.bleepingcomputer.com/news/microsoft/microsoft-outlook-email-sending-issues-for-users-with-lots-of-folders/)