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OWA inline CID images still not displayed – EEMS mitigation side effect persists?
Environment: Exchange Server Subscription Edition (SE), RTM Jun26SU installed (all updates current as of June 2026) On-premises, Windows Server 2019 OWA tested in Chrome, Edge, Firefox – all including InPrivate/Incognito mode Issue: Since approximately May 14–15, 2026 (coinciding with the EEMS mitigation rollout for CVE-2026-42897), inline CID-referenced images in emails are no longer displayed in OWA. Instead, OWA replaces them with a transparent 1×1 GIF placeholder (a data-URI containing a blank GIF image). Microsoft Support confirmed this is a known side effect of the EEMS mitigation for CVE-2026-42897. We expected the June 2026 Security Update (KB5094139) to resolve this – but the problem persists even after installation. Test results: Method OWA Outlook Desktop Thunderbird External HTTPS image ✅ Visible ✅ Visible ✅ Visible Base64 embedded image ❌ Not visible ✅ Visible ✅ Visible CID inline image ❌ Not visible (blank placeholder) ✅ Visible ✅ Visible What we confirmed: Affects all users, all browsers, all devices, all networks Affects newly created mailboxes as well The blank placeholder is injected server-side by OWA Problem started exactly with the EEMS mitigation rollout (~May 14, 2026) June 2026 SU (KB5094139) installed – problem still present Microsoft Support has been engaged for 5+ weeks without resolution Questions: Has anyone else confirmed that the June 2026 SU does not fix the OWA inline image rendering issue? Is there a known follow-up fix or hotfix planned specifically for this side effect? Has anyone found a working workaround that does not involve disabling Extended Protection? Any feedback from the Exchange product team or other admins would be greatly appreciated.SolvedBjoernSJun 23, 2026Tin Contributor1KViews1like7CommentsDisabling Calendar Repair Assistant on mailboxes in Exchange Onprem 2019
Hi, We are in Exchange Hybrid setup were some mailboxes are in cloud and onprem. Recently, there were some issues with Calendar events were recipients weren't notified of any updates for the events, sometimes the updated event would have been cancelled by recipient and the recipient didn't even know that they received update and it was automatically cancelled by them.... This was a normal situation for EAs for their executive calendar events When raised a ticket with Microsoft on this issue, Microsoft collected CDL logs and found that CRA was kicking in each time when there was an update and was reverting the updated meeting request to the previous cancellation and as we know this is not a bug, this is just how the CRA works...So, Microsoft is like CRA is a legacy feature with limited applicability and functionality in the current exchange environment and hence has asked to disable-CRA in On-prem exchange as this will not affect normal calendar usage for users. I had disabled for 5 users and they have reverted that they are not seeing any issues post disabling CRA. so before gunning down on all mailboxes I wanted to take a second opinion on whether is it safe to disable CRA for alll mailboxes in Exchange OnpremSolvedPoorMens_BravoApr 23, 2026Brass Contributor341Views0likes2CommentsIs the Archive mailbox self-help diagnostic working for anyone?
Just curious: is the archive mailbox self-help diagnostic at https://aka.ms/PillarArchiveMailbox working for anyone? When I run it, instead of getting results about the user whose UPN I entered, I get this: The following issues were found with your archive mailbox. No account was found for [The UPN of my admin account]. Make sure you've entered the correct email address or create a new account with that name. For more information, see Add users to Office 365. I tried opening a ticket with Microsoft Support, but they refused to work on it without requiring me to do all the legwork of gathering logs and HAR traces and who knows what else, despite the fact that the support agent was able to replicate the exact same issue in his lab.SolvedRyanSteele-CoVApr 21, 2026Steel Contributor157Views0likes3CommentsDisabling Tenant-Wide Auto-Archiving in Exchange Online
Hello, I need to disable auto-archiving for Exchange Online mailboxes at the tenant level. Before I pull the trigger, I would like to make sure I’m looking at the right knobs and understanding the downstream effects. Where is the definitive On/Off switch for auto-archiving at the tenant level (Admin Center vs. PowerShell)? What is the actual functional difference between the Archive settings in Org Settings and a standard Retention Policy? If I disable the tenant-wide auto-archiving, what happens to the mail that is already sitting in users' archive mailboxes? Does it stay put, or does it try to merge back? Thank you in advance.SolvedIT_BeeMar 18, 2026Tin Contributor248Views0likes3CommentsOAB download fails after hybrid mailbox move.
Hi folks, I'm posting this query here as I doubt anyone in the Outlook forums would have the necessary Exchange hybrid knowledge. I run a classic hybrid Exchange environment where Exchange Server 2019 CU15 is the on-premise platform. Authentication is provided by on-premise AD FS, with the accounts being synchronised from on-premise via AAD Connect. I've just moved my on-premise mailbox to Exchange Online via New-MoveRequest and for the most part, everything is fine. One thing that possibly isn't fine - going off the Bits-Client event log is the regular offline address book downloads, where I'm seeing regular failures in the event log and through double-checking with bitsadmin.exe. The initial address book synchronisation worked as the view in Outlook is fully populated, however, I expect that future changes likely won't come through. bitsadmin output Event log output (There's numerous events to choose from - this is the one I'm most curious about.) The BITS service provided job credentials in response to the UNIDENTIFIED authentication challenge from the outlook.office365.com server for the Microsoft Outlook Offline Address Book <guid> transfer job that is associated with the following URL: /OAB/<guid>/oab.xml. The credentials for the <sid> user were rejected. When the mailbox was on-premise, the OAB came from the Exchange Server - no surprise there, where post migration it can be seen from the bitsadmin output it now comes from outlook.office365.com. Perhaps that's also to be expected - I don't know, but it makes sense given the move. What alerted me to there potentially being an issue is the systray icon frequently gets stuck on the "synchronising" icon, and running a manual full OAB sync from within Outlook fails to complete. After an extended "hang" period, the sync window eventually times out with the error shown above (the protracted UI behaviour would appear to be due to the large number of retries). Dropping the BITS job URL into Edge simply returns a HTTP 503, which doesn't necessarily strike me as a problem. After all, I'm unable to provide a BEARER token using this method. I haven't yet tried via PowerShell as it only occurred to me now but perhaps I'll do so after posting this. Searching on this error and scenario has turned up nothing useful. I have also checked and compared event log entries from an Azure AD-native account, where it's a mixed bag of successful OAB BITS downloads and unsuccessful ones that feature the same symptoms as above, which offers up the possibility this might be a transient service-side error (though I'm not leaning heavily towards this). Has anyone else encountered this issue and resolved it? Is it even an issue to begin with, or is this expected behaviour? I'm unsure what to make of the symptoms. Cheers, LainSolvedLainRobertsonMar 13, 2026Silver Contributor301Views0likes2CommentsProper whitelisting of microsoft.com on dnswl.org
I keep having the issue that system-generated e-mails, e.g. on Trace Reports get classified as spam by the receiving e-mail provider. The sender address is email address removed for privacy reasons and the e-mails go to my M365 mailbox and are redirected to my external monitoring mailbox with that e-mail provider. The e-mail provider calculates a score that includes checking the sender's IP address 52.101.69.91 with dnswl.org . Unfortunately, that address is only whitelisted for outlook.com and some secondary domains, but not for microsoft.com. Of course, the issue also occurs with mailto:email address removed for privacy reasons and other IP addresses, so this is an example. It started to occur around two weeks ago, not sure if the provider changed policies or Microsoft changed the whitelisting; of course the provider refuses to overrun dnswl.org it, e.g. by own whitelisting. Who at Microsoft could I ask to fix that kind of issues? I don't find any appropriate category in their support menues, M365 support says the cannot help (TrackingID#2603031420001611). Thanks in advance for any hints, this is my first posting here, so please forgive me, if this is a dumb question.SolvedVolkerMMar 04, 2026Tin Contributor105Views0likes2CommentsAutoreseed, now what?
Have had a disk failure in a four server Exchange SE DAG with autoreseed enabled. New disk inserted, but now what? What I can google and AI myself to is something like this: Bring the new disk online Remove the broken mount point by deleting the mount point folder that does not lead anywhere Create a New Simple Volume and mount it in an empty NTFS folder Format it as per our standard, ReFS 64K and label to our standard (same as the old one) Does the experts agree that this is all there is to it? Many thanks!SolvedMartenTJan 15, 2026Tin Contributor191Views1like6CommentsUpgrading to Exchange SE
Hi, I currently have Exchange 2019 and need to upgrade to SE. When attempting an upgrade the process didn't appear as expected. Articles I've read basically said the process should be the same as a regular CU upgrade. When I run setup from the ExchangeServerSE-x64 iso, I get an Add Server Role window, instead of the expected upgrade method. The window presents 3 Roles, 2 are ticked, and they're all greyed out. The Next button has no function. I have Standard Edition 15.2 2562.17 (CU15). When checking my build number online, it is listed as the SE version, released July 1st, 2025. When I run Get-ExchangeServer, the Edition = Standard. Should it not say Subscription, or maybe SE? How do I verify my installation is actually SE? ThanksSolvedSteveJDJan 08, 2026Tin Contributor1.1KViews2likes4Comments
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