Users moved to #office365 Exchange Online but on-prem GAL affected


In a recently upgraded hybrid 2010/2013 environment with Single Sign On there can be a problem with the on-premises Global Address List.

Below is how the issue manifests itself for users and what can highlight the issue;

  • As soon as a user is migrated to Office 365 it no longer exists in the on-premises GAL for on-premise users.
  • GAL for the migrated user works fine, it shows both on-premises and O365 mailboxes.

Firstly it would be wise to check the following location in the Exchange Management Console – on-premise

exchmanconsoleYou need to check whether the migrated mailboxes are shown as ‘Remote Mailboxes’ as shown in the screenshot under Recipient Type Detail.

Solution:

The solution for this is to check for any instances of a ‘custom GAL’ – if this is the case then you will need to remove this custom instance as it doesn’t allow on-premise and Office365 to correctly populate the on-premise Global Address List.

About Stephen Pothecary
IT Professional and Cloud Evangelist! IT Manager at Comms Group UK Ltd - Managed Services | Solutions | Procurement | Support Services | Cloud | Fujitsu!

2 Responses to Users moved to #office365 Exchange Online but on-prem GAL affected

  1. Arndt says:

    This might be the solution!
    Do you know how to determine a “custom GAL” in Exchange 2013?
    Running Ex13 in Hybrid mode, getting the same results as described under your issues.

    • A custom GAL will be anything other than the default – so one that has been created outside of the normal/default GAL. To determine you need to see whether you have a default alongside your created within Exchange Management Console

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