Microsoft has reminded commercial customers using older versions of Outlook that they have just two months to upgrade before they're cut off from the company's Microsoft 365 and Office 365 services.

"After November 1, 2021, only Outlook 2013 Service Pack 1 (with latest fixes) and later will be able to connect to Microsoft 365 services," the firm said in an unsigned Aug. 27 post to a company blog.

Last year, Microsoft dropped support for older versions of Office connecting to its online services, such as Exchange Online, as of Oct. 13, 2020. Affected editions of Office included Office 2007, which was already out of all support; Office 2010, which was to exit support on that same Oct. 13 date; and Office 2013, which was to receive support until April 2023. The support-on-services shutdown had been in the works since 2017.

At the time, Microsoft had been surprisingly gracious, saying that while support would officially end, that didn't necessarily mean the end of connectivity. "We won't take any active measures to block other versions of the Office client, such as Office 2013, from connecting to Office 365 services, but these older clients may encounter performance or reliability issues over time," the developer said then.

That is what's different now. The Nov. 1 deadline reallywillcut older Outlook clients from Microsoft's services. Microsoft explained that the older Outlook 2007 and Outlook 2010 clients will be incompatible with two upcoming changes to services, including an end to support for Basic Authentication - essentially, the long-standard username + password combination - that was postponed in February 2021.

Microsoft did not say when it would drop Basic Auth support, however.

For those who haven't yet dispensed with the old Outlook clients, Microsoft recommended - as it has confidently - that they switch to the subscription model of Office 365 or Microsoft 365, which provides always-up-to-date client software.