Microsoft is investigating a bug that causes deleted emails to reappear in the mail inbox of Outlook.com accounts. The company says it’s working on a fix to be deployed when a resolution is available. Microsoft also fixed an issue where images are either corrupted or not visible in emails is also under investigation since August 2020. Earlier today, Redmond has also fixed 503 errors when users attempted to access Outlook, OneDrive, SharePoint Online, and Power BI.com, among other services affected by the bug.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-is-investigating-undeletable-outlookcom-emails/