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Monthly Update #123 Available for Download
The Office 365 for IT Pros author team is pleased to announce the release of the September 2025 update for the Office 365 for IT Pros eBook (2026 edition). As always, subscribers can download the latest EPUB and PDF files from Gumroad using the personalized link included in their original purchase receipt. The Automating Microsoft 365 with PowerShell eBook has also been updated (now at version 15.2), and you can download files for that update from the same place. See our FAQ for more information about downloading updates.
As always, the September 2025 update reflects our ongoing commitment to keeping IT professionals informed and equipped with the most current guidance for managing Microsoft 365. The September release includes updates across almost every chapter, covering recent changes in Teams, SharePoint Online, Exchange Online, and Microsoft 365 security and compliance.
The Microsoft Defender for Office 365 Licensing Question
The most popular articles on the Office365itpros.com site in August were the two-part series covering licensing of shared and user mailboxes when Microsoft Defender for Office 365 (MDO) is active in a tenant. In a nutshell, once MDO is in a tenant, Microsoft requires all user mailboxes and all shared mailboxes to have MDO licenses (or rather, the accounts owning these mailboxes).
By comparison, group mailboxes don’t need MDO licenses, even though they receive exactly the same level of protection from MDO. This inconsistency might exist because Microsoft wants tenants to use group mailboxes instead of shared mailboxes, or it could simply be an oversight.
In any case, the articles sparked quite a debate. Some people felt that we should have left sleeping dogs lying and not mentioned the issue at all. Others told me about true-up exercises done by Microsoft when account teams told customers that they’d have to pay for MDO licenses. To their credit, the MDO team took the criticism to heart and internal discussions are happening within Microsoft. We await the results of those talks and hope that Microsoft will do the right thing and restore consistency and fairness (and not by charging all and sundry for MDO licenses).
Hybrid Connectivity
Relatively few active Exchange mailboxes are now on-premises. Most are now online. There’s no formal count from Microsoft to back this hypothesis, but the numbers of Microsoft 365 paid seats (the latest figure is “over 430 million”), most of whom use Exchange tell a story.
Hybrid organizations with mailboxes remaining on-premises need to transition to a dedicated hybrid connectivity app. Microsoft is making noises that the pace of switchover is slower than they’d like. Perhaps this is something that’s on the “must do when I return from vacation” list for tenant administrators. If it is, make sure that the dedicated hybrid connectivity app is in place in good time before Microsoft switches off EWS (for its own apps) in October 2025.
Come to TEC to Meet Office 365 for IT Pros Authors
If you’re looking for an autumn conference to refresh your knowledge about topics like Entra ID and Microsoft 365, why not come to The Experts Conference (TEC) in Minneapolis (Sept 30-Oct 1), where authors Tony Redmond, Paul Robichaux, and Michel de Rooij will present on automation and scripting best practices. You’ll also see a tremendous line-up of Entra ID talent, as noted by the irrepressible Merill Fernado in this LinkedIn post. To make it even easier for you, here’s a code with a nice discount for TEC.
On to Update #124
As Microsoft 365 continues to evolve, staying current is essential. The Office 365 for IT Pros eBook remains the definitive guide for Microsoft 365 tenant administrators navigating this fast-moving landscape. Whether you’re focused on automation, compliance, or hybrid deployments, this update ensures you have the latest insights at your fingertips.
If you haven’t yet upgraded to the 2026 edition, now’s the time—renewing subscribers get a discount, and the pace of change isn’t slowing down.