New minimum Outlook for Windows version requirements for Microsoft 365
Published Aug 27 2021 09:00 AM 288K Views

*Update added on 11/4/2021

**Update added on 1/12/2022

***Update added on 3/1/2022
****Update added on 3/23/2022


We are quickly approaching the November 1st deadline when the minimum version requirements for connecting Outlook for Windows to Office 365/Microsoft 365 services will change. So, we thought we’d share more information on why we’re doing that. 


After November 1, 2021, only Outlook 2013 Service Pack 1 (with latest fixes) and later will be able to connect to Microsoft 365 services. It’s worth noting here that Outlook 2007, 2010, and Office 2013 versions earlier than 15.0.4971.1000 *and Office 2016 versions earlier than 16.0.4600.1000 aren’t supported now, but we know some customers just can’t quit them. 


Current status


Since our Message Center post last fall, we’ve seen a drop in the usage of the unsupported versions of Outlook for Windows – great job! If you’re still running older versions, please start working on a plan to move by November 1st. 


Our Customer Support team is actively reaching out to tenants that have the most usage on Outlook 2007 and 2010 to help them meet the deadline. If you have questions or concerns about getting all users off these unsupported builds, please reach out to your support teams. 


*As announced, the block will start rolling out on November 1st for users on Outlook 2007 and will proceed in a phased rollout. 


**The block has started rolling out for Outlook 2010 users on January 11, 2022 and will proceed in a phased rollout. 


***The block has started rolling out for Outlook 2013 users (on versions earlier than 15.0.4971.1000) on February 28, 2022 and will proceed in a phased rollout. 


****The block will start rolling out for Outlook 2016 MSI users (on versions earlier than 16.0.4600.1000) & Outlook for Microsoft 365 users (on versions earlier than 16.0.8321.1000) on March 28, 2022 and will proceed in a phased rollout.


**User experience in Outlook


Outlook users will see the following error message in Outlook, when they experience the block that we are rolling out: “Your Microsoft Exchange administrator has blocked the version of Outlook that you are using. Contact your administrator for assistance.” 


New Outlook requirements blog image.png


Please note that once Outlook 2007 or Outlook 2010 is blocked from connecting to Exchange Online, we are unable to restore the ability to connect. Users can immediately start using Outlook on the web through a browser on their Windows (or any other) device. Outlook on the web connects to Exchange Online and allows the user to interact with their email, contacts, calendar, groups, public folders and tasks. 


In order to connect to Exchange Online using Outlook for Windows, the device must be upgraded to a supported version of Outlook for Windows as outlined below.


Customers can also immediately obtain a free 1-month trial of Microsoft 365 Apps for business, which includes the Outlook desktop client to use with their existing Exchange Online subscription. 


Outlook for iOS and Android and Outlook for Mac are other recommended options on mobile devices to connect to Exchange Online and utilize the feature-set offered in our service for mobile users. 


***Outlook 2013 users should see the following error when attempting to connect to a mailbox in Exchange Online using an out of support build of Outlook 2013 after the block is enabled:


User experience in outlook.jpg 

****Outlook 2016 users should see the following error when attempting to connect to a mailbox in Exchange Online using an out of support build of Outlook 2016 after the block is enabled:


New minimum outlook blog - new error message.jpg


Why are we blocking old versions? 


Older versions of Outlook, such as Outlook 2007 and 2010 are incompatible with the following upcoming service changes, which is prompting this controlled block: 

  • Support for basic authentication is ending to increase the security of Microsoft 365 by relying on modern authentication protocols, which are not only more secure, but also provide compliance and policy controls to help you manage your data. 
  • We’re working on adding support for HTTP/2 in Microsoft 365. HTTP/2 is a full duplex protocol, which decreases latency through header compression and request multiplexing. On the service side, we’ll be able to better prioritize requests and more effectively push data to clients. 

It can be a challenge to stay current, but there are many reasons why staying current is a good idea: 

  • Security fixes will protect your devices against known vulnerabilities. 
  • Reliability – over the last five years we’ve eliminated 75% of crashes in Outlook! 
  • Updated versions have all the coolest new features to make your life easier! 



For tenant admins who would like to know what versions of Outlook are active in their tenant, the Email apps usage report provides a full list of all users and Outlook versions in use within a tenant organization. For more information, see Microsoft 365 Reports in the admin center - Email apps usage. 

Upgrade guidance


Continue the conversation by joining us in the Microsoft 365 Tech Community! Whether you have product questions or just want to stay informed with the latest updates on new releases, tools, and blogs, Microsoft 365 Tech Community is your go-to resource to stay connected!

Version history
Last update:
‎Mar 24 2022 10:16 AM
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