Outlook Cache and x500 Addresses when Re-creating On-prem DL Objects in Cloud

Question

Hi

We have an Exchange hybrid deployment. There are around 390 static Distribution Lists (DLs) created on-prem and synchronized to Azure AD / Exchange Online. We're suffering with the well-known issue where the owners of the DLs whose mailboxes are migrated to Exchange Online are unable to self-manage the DLs. To resolve this issue (in a move-forward fashion), we've ultimately decided to remove the on-prem DLs and recreate them in Exchange Online.

We're going to copy over most of the on-prem DL attributes (owner, Primary SMTP, x500 address, members, delegation etc.) to the new DLs in cloud. However, the new cloud-based DLs will be created with a new name. This raises concerns for the Outlook clients' Auto-complete list (nickname cache), which will require reset (as described here--> https://support.microsoft.com/en-us/office/manage-suggested-recipients-in-the-to-cc-and-bcc-boxes-with-auto-complete-dbe46e31-c098-4881-8cf7-66b037bce23e)

I want to clarify the following:

1. My interpretation from the the article above is that Outlook clients newer than Microsoft 365 Version 2202 (Build 14931.20604) that are connected to Exchange will not suffer with the stale entries in Outlook nickname cache. Is this correct?
2. If we copy over the x500 address of the on-prem DLs to the new DLs in cloud, will the outlook clients still require cleanup of the nickname cache?

Thanks

Taranjeet Singh

Answer 1

Beginning with Outlook for Microsoft 365 version 2202, the suggestions list uses Search, but the auto complete cache is still there:

https://learn.microsoft.com/en-us/outlook/troubleshoot/contacts/information-about-the-outlook-autocomplete-list

for Question 2, if you add the X500 addresses to the new DLs, then you should not need to clean up the Outlook cache since that is the reason you are adding the x500.

Answer 2

Thanks for your responses David. So, for point #1, we still need to clean the stale addresses from the Outlook Cache on the Outlook for Microsoft 365 2202 and newer versions?

Although I understand that if we're copying over the x500 addresses, it should fix the issue by itself.