Microsoft postpones new Outlook migration to 2027

"We're extending the opt-out timeline and providing 12 months of lead time as we continue delivering key features and improvements. In other words, new Outlook still doesn't do what many enterprises need, and not enough are at a stage in their migration timelines for Microsoft to move to the opt-out phase."

"Opt-out is where new Outlook is on by default, but can be turned off. It will automatically bring customers into the new experience. However, users and administrators still have the ability to opt out, and policies that disable or limit access to new Outlook will still apply. The next stage, cutover, will mean users will not be able to switch back to classic Outlook."

"Administrators will have at least 12 months of notice before the cutover stage is implemented, meaning there is unlikely to be much in the way of additional postponements after March 2027. Existing installations of classic Outlook through perpetual and subscription licensing will continue to be supported until at least 2029."

Microsoft postponed the opt-out phase for its new enterprise Outlook version to March 2027, extending the deadline by 12 months from the originally planned April 2026. The company stated this delay ensures organizations have adequate time to prepare for migration. In opt-out phase, new Outlook becomes the default but users and administrators can still disable it. The subsequent cutover phase will eliminate the ability to revert to classic Outlook. Classic Outlook will receive support until at least 2029, with administrators receiving minimum 12 months notice before cutover implementation. The postponement suggests slower-than-expected adoption rates and indicates new Outlook still lacks certain enterprise features organizations require.

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