Microsoft has implemented a server-side fix for an issue that prevented some Classic Outlook users from sending emails via Outlook.com and generated NDRs with error code 0x80070005-0x0004dc-0x000524. Affected users are advised to use the New Outlook or Outlook.com on the web or apply temporary workarounds while Microsoft continues investigating related Classic Outlook and Exchange Online issues. #ClassicOutlook #Outlookcom
Keypoints
- Microsoft deployed a service change on April 3, 2026 to fix the Outlook.com send failures for Classic Outlook users.
- Affected users received non-delivery reports (NDRs) showing error 0x80070005-0x0004dc-0x000524 when sending or replying.
- The issue was more frequent when the Outlook.com account was used from a Classic Outlook profile linked to another Exchange account.
- Temporary workarounds include using the New Outlook, Outlook.com on the web, or downloading the Outlook Address Book.
- Microsoft is also investigating other Classic Outlook bugs and intermittent Exchange Online access problems affecting mobile and macOS clients.