Microsoft changing how Outlook connects to Office 365

Microsoft recently announced an upcoming change to their Office 365 (Exchange Online) service that could result in some Outlook users not being able to connect to their mailboxes. We want to make sure our partners around the world are aware of this so that you can prepare yourselves and your customers.  

Overview 

The changes will affect all Outlook users who are not using a 2016 version to connect to an Office 365 mailbox.  The announcement states that the protocol previously used by Outlook 2007, 2010, and 2013 to connect with Office 365 (RPC over HTTP aka Outlook Anywhere) will no longer be supported by Office 365 after October 31, 2017.  Once the changes have been rolled out to Office 365 servers, Outlook will not be able to connect unless it has the required updates to support MAPI-over-HTTP. 

Microsoft support article - RPC over HTTP deprecated in Office 365 on October 31, 2017 

However, this Microsoft update will impact many of your customers who are using Office 365, as well as customers you will be migrating in the months ahead. 

What this change means for... 

Outlook 2007 users - Must Upgrade

Users of Outlook 2007 will not be able to connect to Office 365 beyond October 31. They will therefore need to upgrade to a newer version of Outlook.  

Outlook 2010 users - Must Update

Outlook 2010 will only be able to connect to Office 365 beyond October 31 if updates have been installed to meet or exceed build number 14.0.7164.5002.  

Also important, Microsoft mainstream support for Outlook 2010 has expired. 

Outlook 2013 users  - Must Update

Outlook 2013 will only be able to connect to Office 365 beyond October 31 if updates have been installed to meet or exceed build number 15.0.4779.1002. 

Here’s what to do for current Office 365 customers 

• Verify Outlook versions and build numbers 
  
  
  • Microsoft support article – What version of Outlook do I have? 
  • Most organizations run multiple versions of Outlook, so it’s worth the time to check every user.  
• Notify your customer of any required upgrades

What the Microsoft RPC over HTTP change means for upcoming migration projects 

Customers who migrate to Office 365 before October 31 may initially be able to connect to Office 365, but the connection will be broken when the Microsoft update takes effect. Therefore, it’s recommended that all desktops be upgraded to a compatible Outlook version and build number for all future migrations. (This should be done prior to installing the Outlook Assistant or 48 hours after cutover.) 

Source: https://blog.skykick.com/microsoft-changing-how-outlook-connects-to-office-365