Is anyone else seeing Exchange Online problems in the US Central and Midwest regions? Some internal messages are delayed or failing with errors such as `432 4.2.0 STOREDRV.Deliver.Exception:AgentGrayException.CryptographicException` and `550 5.6.200 STOREDRV.Deliver; message is treated as poison`. In addition to mail delivery failures, some users cannot load Outlook on the web, search is unavailable, and messages accepted through connectors are not appearing in message trace. The impact seems inconsistent—some users or tenants are affected while others are still working normally.
4 Answers
We’re seeing the same thing across our tenant. Internal mail is failing for everyone, and the errors point to a transient transport or cryptographic processing problem. It doesn’t look like an isolated mailbox issue.
The symptoms vary by user and location here. Some messages go through while others are treated as poison with the 550 5.6.200 error. Outlook on the web and search are also failing for several users, so this appears broader than ordinary mail flow delays.
We’re affected too: users can send mail but aren’t receiving anything, and the web client returns a server error during startup. Connector traffic is accepted, but the messages never show up in message trace.
Microsoft has reportedly opened incident EX1464935 for this issue, although it may not immediately appear in every tenant’s service-health view. If your dashboard still shows green, it’s worth checking again later and opening a support case with the exact STOREDRV and poison-message errors.
That matches what we’re seeing in the US Central and Midwest areas. It started intermittently but has become more consistent.