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Microsoft Outlook Classic Teams Meeting Add-in breakage from previous build

Service Disruption
First reported
Last updated
Happening score
H score 0
1 unique sources, 2 articles

Summary

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The Microsoft Outlook Classic email client is temporarily unusable for some users when the Microsoft Teams Meeting Add-in is enabled, disrupting access and email use. Microsoft says the issue stems from a previous Outlook build and is tracking it as EX1254044. Affected users are advised to update Outlook or run an Online Repair for click-to-run installs. Microsoft is also investigating separate classic Outlook connection problems with Gmail and Yahoo accounts.

Related Happenings

Microsoft Exchange Online mail flow disruption

Service Disruption
H score25 First: 02.06.2026 20:02 Last: 02.06.2026 20:02 Sources 1

About this happening: Microsoft is addressing a **widespread Exchange Online service disruption** that is delaying and failing email delivery for customers across **North America** and **Germany**. The...

Open Happening

Microsoft Exchange CVE-2026-42897 mitigation advisory

Advisory/Mitigation
H score44 First: 15.05.2026 12:40 Last: 15.05.2026 12:40 Sources 1

About this happening: **Microsoft** issued immediate mitigation guidance for **CVE-2026-42897**, reducing risk for **Exchange Server 2016, 2019, and Subscription Edition (SE)** on-premises servers that...

Latest development: 15.05.2026 15:35

Microsoft issued temporary mitigation guidance for CVE-2026-42897 while a patch is still in development, recommending the Exchange Emergency Mitigation (EM) Service, which is enabled by default and can be checked with the Exchange Health Checker script, or the Exchange On-premises Mitigation Tool (EOMT) for disconnected or air-gapped environments. Microsoft noted that the mitigations can disrupt features such as OWA Print Calendar and Inline images, and that servers older than March 2023 cannot receive new mitigations through EM Service.

Open Happening

Microsoft Exchange Server spoofing/XSS flaw under active exploitation (CVE-2026-42897)

Vulnerability
H score37 First: 15.05.2026 09:19 Last: 15.05.2026 09:19 Sources 1

About this happening: **CVE-2026-42897** is an **actively exploited** **spoofing** vulnerability in **on-premises Microsoft Exchange Server** that can lead to **arbitrary JavaScript execution** in a br...

Latest development: 09.06.2026 20:57

Microsoft identifies CVE-2026-42897 in Microsoft Exchange Server as an actively exploited spoofing vulnerability that can lead to JavaScript execution in a target’s browser when a specially crafted email is opened in Outlook Web Access under certain interaction conditions. Microsoft says mitigations are being pushed through the Exchange Emergency Mitigation Service while it continues work on the full update.

Open Happening

Microsoft Windows 365 Office installation disruption

Service Disruption
H score0 First: 13.05.2026 14:53 Last: 13.05.2026 14:53 Sources 1

About this happening: The **Windows 365** service update has introduced a **configuration change** that is blocking **Office downloads and installs** for some customers, disrupting access on cloud PCs....

Open Happening

Microsoft Exchange Online blocks legacy TLS for POP3 and IMAP4 starting July 2026

Security Tool/Service
H score11 First: 28.04.2026 16:18 Last: 28.04.2026 16:18 Sources 1

About this happening: **Microsoft** will block **TLS 1.0** and **TLS 1.1** for **POP3/IMAP4** access to **Exchange Online** in **July 2026**, which could break legacy mail clients and embedded devices...

Open Happening

Timeline

  1. 31.03.2026 15:04 1 articles · 3mo ago

    Microsoft rolls out fix for Outlook Classic Teams add-in crashes

    Mitigation Patch Update

    Microsoft resolved the classic Outlook crash issue tied to the Microsoft Teams Meeting Add-in and said a fix is rolling out with Microsoft Teams version 26058.712.4527.9297. Affected users are being told to update classic Outlook to the latest build, run an Online Repair for click-to-run installs, or temporarily disable Microsoft Teams Meeting Add-in for Microsoft Office.

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  2. 17.03.2026 12:37 2 articles · 3mo ago

    Microsoft reports Outlook Classic unusable with Teams Meeting Add-in

    Initial Disclosure

    Microsoft says some users may be unable to use Microsoft Outlook Classic while the Microsoft Teams Meeting Add-in is enabled, with EX1254044 tracking the issue. The company says a previous Outlook build version is causing the impact and advises affected users to update Outlook or run an Online Repair for click-to-run installs.

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