Exchange Online
A cloud-based service included in Microsoft 365, delivering scalable messaging and collaboration features with simplified management and automatic updates.
My error came from internal messages ! ( but also external )
Error: 550 5.6.200 STOREDRV.Deliver; message is treated as poison
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(118.4, 81%, 21%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EMN%3C/text%3E%3C/svg%3E)
Marton, Norbert
0
Reputation points
Hi,
A user has issues receiving email, i checked the Message Trace and this is what i did found - could someone explain what this should mean ? ( We are using Exchange Online - not on prem )
Reason: [{LED=550 5.6.200 STOREDRV.Deliver; message is treated as poison.}
Exchange Online
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(259.20000000000005, 99%, 35%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ERJ%3C/text%3E%3C/svg%3E)
Richard J. Phippen 25 Reputation points2026-08-31T16:46:07.0533333+00:00 I have multiple clients across different tenants reporting the same thing.
550 5.6.200 STOREDRV.Deliver; message is treated as poison
This is happening with standard gmail accounts, as well as government and reputable company domains.
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(201.6, 33%, 29%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ECS%3C/text%3E%3C/svg%3E)
Cameron Shove 0 Reputation points2026-08-31T17:04:59.35+00:00 We're getting the same. Appears to be enterprise wide regardless of sender (so far). Microsoft happened to report an Exchange Online service issue this morning but cleared it as a false positive. https://admin.cloud.microsoft/?#/servicehealth/:/alerts/EX1464935
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(220.8, 56.00000000000001%, 31%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EH%3C/text%3E%3C/svg%3E)
Hendrix 990 Reputation points Independent Advisor2026-08-31T17:23:35.7533333+00:00 Hi Norbert,
Based on my research, likely as Cameron said, this issue turns out to be related to a Microsoft service degradation, EX1464935, that affects multiple services related to Exchange Online. At this time, no additional troubleshooting is required on your side.
I recommend contacting your IT administrator and asking him/her to monitor incident EX1464935 in the Microsoft 365 admin center > Service Health for the latest updates, as Microsoft is actively working on a resolution.
Also, as many members of the community may not yet be aware of this incident, I hope you find this information helpful. Sharing or highlighting this response can help bring greater visibility to the issue, making it easier for others who are experiencing similar challenges to find relevant information and support.
Thank you for your patience and understanding. I wish you a wonderful day ahead.