Timeline for Classic Outlook
Microsoft has outlined a phased, multi-year rollout for replacing Classic Outlook with the New Outlook:
📅 Key Dates You Should Know
By April 2026
Microsoft plans to start transitioning commercial (M365 Business & Enterprise) users into an “opt‑out” stage, where New Outlook becomes the default, but users can still switch back to Classic Outlook Microsoft Answers+15PCWorld+15bitrecover.com+15.
Early 2028
A “cutover” phase begins—New Outlook becomes mandatory. Classic Outlook is removed from standard Microsoft 365 installations (though standalone/downloadable versions may still be obtainable) TECHCOMMUNITY.MICROSOFT.COM+2Directions on Microsoft+2Microsoft Answers+2.
Q2 2029 (approx. April 2029)
Support for Classic Outlook officially ends. After this, there will be no more updates, security patches, or technical assistance for it Directions on Microsoft+2bitrecover.com+2cubexsoft.com+2cubexsoft.com.
🧭 Summary Timeline
✅ What This Means for You
You can safely continue using Classic Outlook through 2025 and beyond—it won’t stop working yet.
Beginning April 2026, you'll likely be switched to New Outlook by default, but you’ll still have the choice to revert—for now.
Starting 2028, Classic Outlook will no longer be included in main Microsoft 365 installations, but you may still be able to install it separately.
After April 2029, Classic Outlook hits end-of-life—continued use will carry security and compatibility risks.
💡 Recommendations
Plan your transition early. Test any workflow or add-ins that are critical to your productivity to ensure compatibility with New Outlook.
Back up data (e.g. export PSTs) so you're prepared for the eventual shift.
Train your team on New Outlook features between now and 2026–2028 to make the cutover smoother.