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Images are not shown in OWA, but are shown in Outlook for Desktop

DimitarVTomov-0973 0 Reputation points
2026-06-16T08:52:46.19+00:00

Hello,

We are experiencing a problem where an image in the body of the mail is not visible in OWA. The image is visible in Outlook for Desktop. The image is being sent by a user within the organization. The issue appears for multiple users, on different browsers from inside and outside of corporate network. Once you click reply / forward the image is shown in OWA.

Exchange is on prem.

Exchange | Exchange Server | Other
Exchange | Exchange Server | Other

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  1. Michelle-N 18,605 Reputation points Microsoft External Staff Moderator
    2026-06-16T09:43:49.25+00:00

    Hi @DimitarVTomov-0973

    Based on the details you shared, I understand that inline images in the body of emails sent by internal users are failing to display in Outlook on the Web (OWA), even though they render perfectly fine in the Outlook Desktop client. This issue affects multiple recipients across different web browsers, regardless of whether they are accessing OWA from inside or outside the corporate network. Interestingly, the missing images suddenly become visible as soon as the user clicks "Reply" or "Forward."

    After researching this behavior, this specific symptom is heavily linked to a known issue introduced by a recent security mitigation on Exchange Server backend environments. To narrow this down, could you please let me know which version of Exchange Server your organization is currently running? (e.g., Exchange Server 2016, Exchange Server 2019, or Exchange Server Subscription Edition).

    Depending on your specific Exchange Server environment, here are the steps to address this rendering bug:

    • If you are running Exchange Server 2016 or Exchange Server 2019: Only customers who enrolled in the Period 2 Extended Security Update (ESU) program are eligible to receive Exchange Server 2016 and 2019 security updates released between May and October 2026.
    • If you are running Exchange Server Subscription Edition (SE): If your organization has already transitioned to Exchange Server SE, the recommended path to fix this behavior is to safely remove the temporary mitigation script and immediately apply the June 2026 Security Update (SU).

    For full, step-by-step instructions on how to safely manage the mitigation or apply these updates on your session hosts, please refer to the official Microsoft Tech Community and Exchange Server update documentation regarding recent Security Updates.

    https://techcommunity.microsoft.com/blog/exchange/released-june-2026-exchange-server-security-updates/4524491

    Please pass this information along to your Exchange IT Administrator so they can check the patch level of your mail servers. Let me know if you need help finding the specific download links for the updates!

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".  

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  2. AI answer

    2026-06-16T08:53:03.51+00:00

    Based on the description (Exchange on-prem, internal sender, image not visible in OWA but visible in Outlook for Desktop, appears for multiple users/browsers, and becomes visible when replying/forwarding), this most closely matches known OWA/Exchange image-handling bugs that are fixed in later cumulative updates.

    For on-premises Exchange, there are two relevant patterns in the provided material:

    1. OWA inline images and attachments not visible for certain accounts (Exchange 2019)
      When Download Domains are configured and the mailbox alias starts with specific characters (for example, oma*), inline images show as broken icons and text attachments fail with “page not found” in OWA, while the same content is otherwise present. This is resolved by installing the latest cumulative update for Exchange 2019.
    2. Signature images not visible to recipients (Exchange 2016)
      In Exchange 2016, images inserted as data URIs in OWA signatures are not promoted to inline images, so many clients cannot display them. This is also resolved by installing a later cumulative update.

    Although the exact symptom details differ, both issues are caused by defects in how Exchange/OWA handle inline images and are resolved only by applying the appropriate cumulative update.

    Given that:

    • The problem is specific to OWA (desktop Outlook renders the image correctly).
    • It affects multiple users and browsers, inside and outside the network.
    • The image appears when replying/forwarding (OWA re-renders the body differently in compose mode).

    The most appropriate remediation is to:

    1. Identify the exact Exchange Server version and role hosting OWA
      Check whether the environment is Exchange 2016 or 2019 and what cumulative update level is installed.
    2. Update to the latest cumulative update for the corresponding Exchange version
      • For Exchange 2019, install Cumulative Update 15 or later as documented in the OWA inline image/attachment issue.
      • For Exchange 2016, install Cumulative Update 11 or later as documented in the OWA signature image issue.
    3. Retest OWA after the CU update
      After updating, test with:
      • A new message containing the inline image sent between internal users.
      • OWA access from different browsers and networks.

    If the environment is already at or beyond these CU levels, further investigation would focus on whether the specific scenario (for example, Download Domains configuration or data-URI style images) matches one of the documented bugs and whether any additional newer CU addresses related OWA rendering issues.

    References:

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