Exchange/Outlook attachment rendering issue

Matt Farrell 0 Reputation points
2026-10-13T18:37:29.78+00:00

For one Exchange Online user, messages containing multiple attachments intermittently fail to render the attachment expansion control in the Outlook Reading Pane. The attachment count is shown, but the expansion chevron/control is absent. Opening the same message in a separate pop-out window consistently displays all attachments. The problem reproduces in Outlook desktop, Outlook on the web, and OWA InPrivate/Incognito, but another account on the same workstation (logged in as a different Windows user) does not reproduce the issue. Resetting local Outlook/WebView2 cache did not resolve it, neither did a reinstall or clearing the EBWebView folder in AppData/Local/Microsoft/Olk.

Outlook | Windows | New Outlook for Windows | For business
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  1. Elena-VH 2,130 Reputation points Independent Advisor
    2026-10-13T18:59:01.8966667+00:00

    Dear Matt Farrell,

    Thank you for the detailed troubleshooting information. The issue occurs in Outlook desktop and Outlook on the web (including InPrivate/Incognito mode); however, it affects only this specific mailbox, while another account on the same computer works correctly.

    Since resetting the local Outlook/WebView2 cache, clearing the EBWebView folder, and reinstalling Outlook did not resolve the issue, and the behavior is reproducible in both Outlook desktop and Outlook on the web (including InPrivate/Incognito sessions), the issue appears more likely to be related to the mailbox or a service-side rendering problem.

    If you are using a Microsoft 365 work or school account, I recommend contacting your Microsoft 365 administrator and asking them to create a support ticket with Microsoft through the Microsoft 365 Admin Center for further investigation.​ ‌Microsoft Support can perform backend checks on the affected mailbox and review service-side logs that aren't available through standard troubleshooting. For reference: Get support for Microsoft 365 for business and How do I find my Microsoft 365 admin?

    Note: Please understand that as this is a public community forum, no one here has access to your Microsoft 365 tenant, mailbox data, or Microsoft's internal service diagnostics.

    In the meantime, there are some things I recommend you check again: ​‌

    • Step 1: Test the affected mailbox from a completely different device and network​‌
    • Step 2: Check whether the problem affects all messages with multiple attachments or only specific messages​‌
    • Step 3: Review whether any mailbox-level add-ins, information protection labels, transport rules, or third-party email security products are modifying affected messages.

    If you have any questions or if I have misunderstood anything, please feel free to reach out. Looking forward to your update.

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