[German]Brief information or reminder for administrators whose users are using macOS and rely on Microsoft 365 applications. Legacy support for Outlook on the Mac will expire in October 2025. This has implications if Outlook is to access mailboxes from on-premises Exchange server installations.
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A reader's note on the end of support
Microsoft also offers Office for Mac (purchase version) and the subscription version Microsoft 365 for Mac for Apple's macOS operating system. Some users will also use this and manage their emails via Outlook. Blog reader Micha sent me an email the other day pointing out an issue that had somewhat passed me by (thanks for that).
Outlook legacy support ends Oct. 2025
Micha informed me in his email about the discontinuation of legacy support for Microsoft Outlook for Mac. Microsoft has made the whole thing public as of January 31, 2025 under MC994282 – Legacy Microsoft Outlook for Mac: Support will end – as a tenant administrator, he received an email with the corresponding notification. 
From October 2025, Microsoft 365 subscriptions linked to a Microsoft 365 account (personal, work or school) will no longer be able to use the old Microsoft Outlook for Mac, according to the announcement. Of course, Microsoft goes on to say that this change is an important step towards a more robust, feature-rich and secure email experience for all users (please don't laugh).
New Outlook should be used
Microsoft writes that the latest version of Outlook for Mac has been part of the Microsoft 365 suite for four years. More than 95% of Microsoft 365 users have already switched from the old version of Outlook for Mac to the new version. Information can be found here and in the Microsoft 365 Roadmap for Outlook for Mac.
What does the end of legacy support mean?
Microsoft writes that organizations still using the older Outlook for Mac will be automatically switched to the new Outlook for Mac via their tenants. No administrative action is required on the part of administrators.
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IT should inform users
However, IT should inform users and adapt the relevant documentation, as users will no longer be able to switch back to Outlook for Mac after this change.
Issue with Exchange (On-Premises)
The above announcement can be shrugged off as "let's just switch to the new Outlook for Mac". Blog reader Micha wrote to me that the new Outlook for Mac cannot access on-premises installations with Microsoft Exchange Server if the instance is not publicly accessible.
Micha concluded his email with the information "For our publishing house and me as admin, this means that Office 365 for MAC without internal email connection will be available from November". He noted that this could also be interesting for many other mixed environments, which is why I'm posting it here. Does anyone else in the readership see themselves affected?
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