[German]Microsoft has confirmed a problem in Outlook which leads to the mail dispatch being canceled. This may be due to the fact that the user has created a large number of folders in the mailbox. In the event of an error, the error 0x80040305 is returned.
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Error report in the Microsoft forum
In the Microsoft Answers forum there is the forum post Error is [0x80040305-0x00000000-0x00000000]. Failed to upload attachments to server (error 0x80040305). Submit-message failed: message id(8), failure enum(29), HResult(0x80040305), EC(0). from October 30, 2023, in which a user describes his problem.
I have a user who is receiving random bounceback messages to internal and external people. The error is [0x80040305-0x00000000-0x00000000]. Attachments could not be uploaded to the server (error 0x80040305). Transmission of the message failed: message id(8), failure enum(29), HResult(0x80040305), EC(0).
However, there is no solution proposed in the Microsoft Answers forum. Also in this forum post at Microsoft Q&A a user in May 2023 describes this error as follows:
Error in Outlook client: Your message did not reach some or all of the intended recipients
I have one user who constantly gets the error in the title. He tries sending an email, then receives an automated email from the System Administrator saying his was undeliverable with the following details:
This message could not be sent. Your server administrator has limited the number of items you can open simultaneously. Try closing messages you have opened or removing attachments and images from unsent messages you are composing. Try sending the message again later, or contact your network administrator.
Diagnostic information for administrators:
Error is [0x80040305-0x000004de-0x0000054a].
Submit-Message failed: message id(2), failure enum(6), HResult(0x80040305), EC(0).
He then must close Outlook and relaunch it and attempt to send the email again, which often will work.
Following some advice I found online, I tried turning off 'download shared folders' which appeared to resolve the issue for a couple of months, but it has recently started reoccurring and is worse than before (happening 5+ times a day).
He has no additional mailboxes that he uses. He has tried using a different laptop and the issue has followed him. I have checked the Event Viewer and no errors or warnings are coming up relating to Outlook or Exchange. I have asked him to try launching Outlook in Safe Mode and he says the behavior is the same. However it does not occur when he uses the web client. Creating a new profile in the Outlook client appears to provide very temporary relief.
A Microsoft employee writes at the end that there are many indications that a broken PST file is causing this effect.
Microsoft confirms the error
On December 7, 2023, Microsoft published the support article Emails sent using Outlook Desktop results in Non-Delivery Report [0x80040305-0x00000000-0x00000000] for Microsoft 365. There the error is acknowledged and it says: When you use Outlook Desktop to send an email, you receive an unexpected non-delivery report (NDR) that contains the error code 0x80040305. Microsoft gives the following example of the error message:
Your message did not reach some or all of the intended recipients.
Subject: Email subject
Sent: 12/7/2023 3:17 PM
The following recipient(s) cannot be reached:
recipient@contoso.com on 12/7/2023 3:17 PM
This message could not be sent. Try sending the message again later or contact your network administrator.
__________________________________________________
Diagnostic information for administrators:
__________________________________________________Error is [0x80040305-0x00000000-0x00000000].
Submit-Message failed: message id(1), failure enum(1), HResult(0x80040305), EC(1246).
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Microsoft writes that this problem is similar to the previous 500-folder limit. However, the Outlook team fixed this issue by removing the 500 folder limit in Outlook. The previous solution applied to shared folders, but not to the scenario that occurs in the user's main mailbox.
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The Outlook team is investigating the issue and will provide further details as soon as the cause is clear and a solution becomes available. For those affected, Microsoft has suggested the following workaround:
- Reduce the number of folders that have subfolders to under 500. We recommend having no more than 450 nested folders while we investigate further.
- Keep folders collapsed (in the inbox) instead of showing them expanded in Outlook.
For those who cannot do any of the above, avoid certain online actions in Outlook. These actions include using the "Show on server" and "Click here to see more information about Microsoft Exchange" buttons or using "Include older results" when searching. If one of these actions is attempted anyway and the error occurs, restart Outlook immediately to achieve optimum performance. (via)
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