Email attachment issues with user after migration to M365 Bussiness subscrption

Question

Email attachment issues with user after migration to M365 Bussiness subscrption

TRaG 190

We are facing some issues with the email attachments on both OWA and Desktop apps for some users where in these users were recently migrated from google workspace, they are not able to open or download the attachments using Microsoft 365 Business subscription on M365 admin portal, suggest

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Answer 1

Helen Luu 3,300 Independent Advisor

Hello @TRaG

Regarding the issue where users are unable to open or download attachments in both Outlook on the web and Outlook desktop, could you please provide the exact error message that the users are receiving?

Additionally, could you confirm whether the issue occurs with all attachment types, such as Word, Excel, PowerPoint, PDF, ZIP files, etc. or only specific file types?

Could you also help check the following:

Are you using New Outlook or Classic Outlook? If possible, please share the Outlook version/build information as well.
Does the issue occur with newly received emails that contain attachments, or only with emails that were migrated from Google Workspace?
Are users able to preview the attachments, or do they receive an error message when attempting to preview them?
- If possible, please provide a screenshot of the behavior or error message.
- Before sharing, please ensure that any personal or sensitive information is blurred or removed.
Are users able to download the attachments using the Outlook mobile app?

The above information will help me determine whether the issue is related to Outlook, Exchange Online, or the migration process itself.

Thank you, and I look forward to your update.

TRaG 190 Reputation points

2026-09-22T06:50:54.8+00:00
Thanks,

Here are the answers

Are you using New Outlook or Classic Outlook?-----Both

Does the issue occur with newly received emails that contain attachments, or only with emails that were migrated from Google Workspace?----New emails

Are users able to preview the attachments, or do they receive an error message when attempting to preview them?----NO

Errors I will generate and send you soon

Are users able to download the attachments using the Outlook mobile app?------- Not checked
TRaG 190 Reputation points

2026-09-22T07:32:55.3466667+00:00

need to add here, which might help

Migration was done using Exchange IMAP only

preview attachments shows

Created a test user mailbox on same tenant its works fine with attachment
Helen Luu 3,300 Reputation points Independent Advisor

2026-09-23T14:03:56.2833333+00:00

Hello @TRaG

Since this issue appears to be related to your tenant configuration and may require a more in-depth investigation, I would recommend reaching out to Microsoft Support directly. The support team has access to internal diagnostic tools that can help determine whether there are any account-related issues or configuration conflicts within the tenant that may be causing this behavior.

To create a support ticket, please follow the instructions provided in the following article: Get support - Microsoft 365 admin | Microsoft Learn

When opening the support request, please make sure to disable the Support Assistant (AI) in the Help panel first. After that, enter a brief description of the issue. Once the AI assistant is turned off, the Contact Support option should become available, allowing you to submit a support ticket directly to Microsoft's support team.

Please give this a try and let me know if you encounter any difficulties during the process. I will be happy to assist further where possible.