Microsoft is urging customers still on Outlook 2007 and Office 2007 to upgrade as each of the products ran out of extended support on Tuesday.
That means no more security updates, feature updates, support or technical notes for the products, which Microsoft has supported for the past decade.
Microsoft wants customers on Office 2007 to plan to migrate to Office 365 in the cloud or to upgrade to Office 2016.
Office 2007 introduced Microsoft's "ribbon" interface that brought a series of tabbed toolbars with each ribbon containing related buttons.
For customers that have already use Office 365 that still use Outlook 2007, it will be important to upgrade by the end of October, after which the product won't allow users to access Exchange Online mailboxes though the Office 365 portal.
"Customers who use Office 365 will have noted that there is a change to the supported client connectivity methods. Outlook Anywhere is being replaced with MAPI/HTTP. Outlook 2007 does not support MAPI/HTTP, and as such will be unable to connect," Microsoft highlights in a send-off note for the email client.
Come October 31, Microsoft will drop support for the RPC over HTTP protocol, also known as Outlook Anywhere, for accessing mail data from Exchange Online. The new protocol, MAPI over HTTP, is sturdier and supports multi-factor authentication for Office 365, according to Microsoft. Microsoft didn't backport the protocol to Outlook 2007 as it would be past its extended support date by the time it cut off Outlook Anywhere.
Microsoft has a full list of Office 2007 products and their exact cut off dates here and Outlook 2007 here.
Unlike previous years Microsoft is not offering enterprise customers extended support for Office 2007 through its custom support contracts.
The same goes for its other Office products, including Exchange Server; Office Suites; SharePoint Server; Office Communications Server; Lync Server; Skype for Business Server; Project Server and Visio.
Microsoft said demand for custom support has declined with greater adoption of Office 365.