IncomingEmailRejected error when attempting to install Dynamics 365 App for Outlook


Symptoms


When you attempt to install Dynamics 365 App for Outlook, the Status column shows "Issue when adding to Outlook". When you click the "Learn more" link, you see a dialog with the following details:

There was an issue when attempting to add the app to Outlook. 
Crm   :   IncomingEmailRejected

Cause


This error can occur for one of the following reasons:
  1. The email address for the mailbox record in Dynamics 365 has not been approved. 
  2. The Exchange mailbox is currently linked to another Dynamics 365 organization.  An Exchange mailbox (email address) can only synchronize appointments, contacts, and tasks with one organization, and a user that belongs to that organization can only synchronize appointments, contacts, and tasks with one Exchange mailbox.  Click here for additional information.    

Resolution


Verify the email address for the Mailbox is approved and associated with the desired Dynamics 365 organization.

  1. Sign in to Dynamics 365 as a user with the System Administrator role.
  2. Click Settings and then click Email Configuration.
  3. Within the Email Configuration area, click Mailboxes and then change the view from My Active Mailboxes to Active Mailboxes.
  4. Select the Mailbox record that encountered the error and then click Approve Email.
  5. After the email address has been approved, click the Test & Enable Mailboxes button.
  6. Within the Test Email Configuration dialog, make sure to select the option Sync items with Exchange from this Dynamics 365 Organization only, even if Exchange was set to sync with a different Organization and then click OK.
  7. After the mailbox has completed testing, attempt to install Dynamics 365 App for Outlook again. This can be located by clicking Settings and then clicking Dynamics 365 App for Outlook.