Outlook broke after Office 365 update to 16.0.19328.20158 – cannot open emails Windows Server 2016
Hello everyone, posting to report that after the latest automatic update to Microsoft Office 365 version 16.0.19328.20158, we are experiencing a critical issue on multiple company machines running Windows Server 2016: The Outlook desktop application launches normally, but when trying to open any email, the following error appears: “There was a problem opening this item... The text formatting command is not available... Reinstall Microsoft Outlook.” Launching Outlook in safe mode (Outlook /safe) does not help. Creating the FORMS2 folder (suggested workaround) does not fix it. Attempting a downgrade via OfficeC2RClient.exe fails with error 30183-27 (400). Quick/online repair from Control Panel also has no effect. In our environment, this issue appeared simultaneously on many workstations and servers, right after the Office update today. Temporary solution: We are instructing users to access their mail via Outlook Web App (OWA), which is not affected by this bug. We would like to know: If others have experienced this bug with this build, including on Windows Server 2016 If any working workaround exists, or an official fix timeframe from Microsoft Thanks to anyone who can share their experience or updates!Replying to emails from M365 Outlook group
A problem I am stumped with, so I am reaching out for some help/guidance. One group wants to not have the emails going into their own inbox but manage and reply only from the group inbox itself (so they know the email has been processed by deleting it once replied). It worked OK to begin with and then some users couldn't reply, then more. Some still can. I have tried reindexing local copy, using browser instead of app & changing the send on behalf of permissions. Owner or member of group doesn't seem to make a difference. Error messages include "This message can't be sent because it no longer exists. It can only be discarded. Make sure you copy the contents of the message before you discard if you want to use them later." and "Couldn't send this message". Please see screenshots attached. My questions: 1: Is Outlook on M365 designed to allow users to reply from the group either as the "group" or as themselves? Information I found isn't clear. 2: If it is / can be - what can I do to make it work for all users? Thanks!How to Check if Shared Mailboxes Need MDO Licenses
Shared mailboxes might need Microsoft Defender for Office 365 licenses, but how do you identify how many licenses? We use PowerShell to do the job by analyzing external email sent to shared mailboxes. If a mailbox receives external email, then by definition the mailbox receives benefit from MDO, and that’s the test for requiring a license. https://office365itpros.com/2025/11/25/microsoft-defender-for-office-365-3/Microsoft Launches Preview of Exchange Admin API
Microsoft launched the preview of the Exchange Admin API on November 17. The new API is intended to close known feature gaps that exist in the Graph APIs and allow developers to migrate from EWS before Microsoft retires EWS in October 2026. Think of the Exchange Admin API as a discardable time-limited API that allows clients to submit cmdlets for processing. It’s certainly one way to approach the EWS problem! https://office365itpros.com/2025/11/18/exchange-admin-api-preview/
Outlook Encrypted Email Issues
I have deployed M365DLP controls to block password protected atachments that cannot be scanned and am telling users to use Outlook Encryption instead to protect outgoing email attachments. However, a number of external companies have reported not being able to open the encrypted messages and the screenshots provided show that they are trying to authenticate as a guest user in my Entra ID instance (rather than using their own IdP, SSO or an OTP). What would cause that and how do I resolve?
Title: Expose SHA-256 or SHA-1 for Mail Attachments in Microsoft Graph
Problem Email attachments in Graph don’t include a content hash. To identify or match attachments, developers have to download the entire file first. That wastes bandwidth and time and increases exposure. OneDrive/SharePoint already return hashes, but mail does not, so experiences are inconsistent. Request Add a server-provided content hash to every mail attachment. Prefer SHA-256. If that’s not feasible initially, expose SHA-1 as a minimum to align with existing Drive item hashes. Benefits Faster and cheaper: avoid downloading large files just to tell if you already have them. Deduplication: detect repeated attachments across threads and mailboxes. Security operations: correlate attachments with threat intel by hash and triage suspicious emails without fetching payloads. eDiscovery and compliance: confidently match the same document across mail and files. Consistency: a predictable, uniform approach across Mail and OneDrive/SharePoint.Office 365 Message Attribution
When a message arrives at Office 365, one of the first things we need to do is figure out which organization it belongs to. At first, this sounds simple – just look at the recipient, right? Well, it is more complicated than that, because of Hybrid and complex routing scenarios.
