Microsoft has warned Mac subscribers of Office 365 that they have to be running either macOS Sierra or macOS High Sierra next week when the company updates the productivity applications.

"As of an Office 365 for Mac September 2018 update, macOS 10.12 or later can be update for your new version of this Office client apps for Mac and receive new feature updates," Microsoft announced in a very support document.

Microsoft will likely deliver the Office 365 September update around September 11 or 12 no matter if sticks for your usual monthly refresh schedule.

At the same time, the Office applications - Word, Outlook, Excel and PowerPoint - will be updated from their current Office 2016 designations toward the new Office 2019 labels, as long as the suite is running upon a Mac run by macOS 10.12 (Sierra) or 10.13 (High Sierra).

Those people who are not continues to receive Office security updates and may no longer get new feature updates. The equivalent caveat will apply generally if the user declines the September refresh to Office 2019: No additional features will be offered the applications.

Previously, Microsoft asserted Office 2019 for Mac - the "perpetual" license version of the suite - would be supported on only two latest editions of macOS. Office 365 for Mac sports exactly the same requirement.

Once Apple releases macOS 10.14, a.k.a. "Mojave," this fall, Office 2019 and Office 365 need to be running on systems operated by that edition, or its predecessor, High Sierra, to have new feature updates.

"When a fabulous version of macOS is released, Office 2019 for Mac's ... requirement becomes the then-current two most recently released versions at the moment: the new version of macOS and the previous version," a Microsoft FAQ said. But because Apple's policy could be to support the newest sort of macOS and the two previous versions, you will find there's Macs that always receive computer system security updates but which do not be with Microsoft with new Office features.

Per analytics vendor Net Applications, last month macOS Sierra and High Sierra made up a combined 78% regarding Mac user share.