Custom address list not syncing to O365 in hybrid environment

Question

hi

Please advise me for an issue where Custom address list not visible into O365 mail box address book in hybrid environment.

or more clear--

The custom address list created in On prem Exchange 2019 and need to be visible on O365 mailbox Address list, currently its not showing, only default global address list visible in O365

we have Exchange server 2019, Entra connect and office365 environment configured with Hybrid configuration,

Answer 1

Address lists are not synchronized, this is by design. There is the "Organization configuration transfer" option you need to select when running the HCW to trigger a one-time sync. This is a one-time operation, if you make any changes, you must rerun the HCW with said option selected. Refer to the FAQ section of this article for additional details: https://learn.microsoft.com/en-us/exchange/hybrid-configuration-wizard-choose-configuration-feature#frequently-asked-questions

In general, you should be managing address lists/policies in ExO when in hybrid.

Answer 2

Hi noventiq

Thank you for reaching out to Microsoft Q&A forum

As states in Address lists in Exchange Online and Choose Exchange Hybrid Configuration, in an Exchange 2019–Exchange Online hybrid, custom Address Lists (ALs) created on‑premises do not sync to Exchange Online. Directory synchronization (via Entra Connect) copies recipient objects (users, groups, contacts) but not on‑prem address list definitions.

That said, as a result, cloud mailboxes only see the Default Global Address List unless you build equivalent GAL/ALs in Exchange Online and (optionally) assign them through Address Book Policies (ABPs) to segment visibility.Therefore, you can try the following approach to see if it can resolve your concern:

1) Add the Address Lists RBAC role to a role group you use (e.g., Organization Management) so the cmdlets New-AddressList, New-GlobalAddressList, Get-AddressList, etc., are available:

Connect-ExchangeOnline
# Example: create a dedicated role group and grant yourself access
New-RoleGroup -Name "Address List Management" -Roles "Address Lists" -Members ******@contoso.com

2) Translate your on‑prem filter to an Exchange Online RecipientFilter

# Custom Address List (users in a region)
New-AddressList -Name "Users - Karnataka" `
  -RecipientFilter "(RecipientType -eq 'UserMailbox') -and (StateOrProvince -eq 'Karnataka')"
# Segmented Global Address List (e.g., by CustomAttribute15)
New-GlobalAddressList -Name "GAL - Sales" `
  -RecipientFilter "CustomAttribute15 -like '*Sales*'"
# Additional lists you might need for ABP components
New-AddressList -Name "Rooms - Sales" -RecipientFilter "(RecipientTypeDetails -eq 'RoomMailbox')"

Link references:

• Create a global address list in Exchange Online
• New-GlobalAddressList
• Address lists in Exchange Online

Hope my answer will help you, for any further concern, kindly let me know in the comment section.

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Answer 3

In a hybrid Exchange environment, if your custom on-premises address list is not syncing to Office 365, consider the following steps:

1. Verify Directory Synchronization: Ensure that Microsoft Entra Connect is functioning correctly. This synchronization is essential for replicating objects, including address lists, from your on-premises Exchange to Office 365. Check the synchronization status and logs for any errors.
2. Check Address List Configuration: Confirm that the custom address list is properly configured in your on-premises Exchange. It should be mail-enabled, and the necessary permissions must be set to ensure visibility in the global address list (GAL).
3. Review Hybrid Configuration: Examine your hybrid configuration settings to ensure they are set up to allow synchronization of address lists. Running the Hybrid Configuration Wizard again may help confirm that all settings are correct.
4. Force Directory Synchronization: If everything seems correctly configured, try forcing a synchronization using the Microsoft Entra Connect tool. This action can sometimes resolve issues where changes are not appearing in Office 365.
5. Inspect for Filters: Check for any filters that might be preventing the custom address list from syncing. Filters can sometimes inadvertently exclude certain objects from the synchronization process.

If these steps do not resolve the issue, further investigation into logs or contacting Microsoft support may be necessary to identify the underlying problem.