Microsoft

Office 365 – Disabling MAPI Includes Unexpected Results

Just a quick FYI in this post…
Exchange Online allows for a fair amount of customization however there are still a few items here and there that can be done in on-premises Exchange but not in the cloud.
Recently, I’ve had a couple clients interested in blocking their users from using Outlook or a specific version of Outlook. In on-premises Exchange, the “Set-CASMailbox” cmdlet has a parameter called “MAPIBlockOutlookVersions” that can be used to achieve this; unfortunately, Exchange Online does not have this parameter.
The next thought was that the “MAPIEnabled” parameter could be used to block Outlook; this setting is actually what is set on users with an Office 365 “Kiosk” license which does not allow for connectivity via Outlook.
While “MAPIEnabled” does in fact block Outlook, it also causes some unexpected changes to Autodiscover…

Disabling MAPI, in both on-premises and the cloud, changes the Autodiscover response for the mailbox. While Autodiscover will still complete successfully with MAPI disabled, you’ll notice that the EWS URL for the mailbox is not returned in the XML response.
As a result, applications trying to use Autodiscover and EWS may fail on mailboxes with MAPI disabled unless the EWS URL is somehow hard-coded in the application. It would not be uncommon for an application to try and use EWS via Autodiscover, applications such as Cisco Unity Connection and BlackBerry Business Cloud Services (BBCS) both do this.
You can confirm the missing EWS URL via the Microsoft Remote Connectivity Analyzer. When running the Exchange Web Services test, you’ll receive the following response:

No EXPR or EXCH settings were found in the Autodiscover response.

 
Just an FYI should you decide that disabling MAPI is a setting you choose to implement.
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