As office 365/Exchange online administrators, We all know that Dynamic Distributions lists are not synchronized via AAD synchronization or you can say not supported, either you have to create the Dynamic DLs in the cloud environment or create a mail contact for each dynamic DLs and point it to on-premise DLs.
Creation of Dynamic Distribution Lists on Exchange online is not always an option if your Dynamic Lists are based on Non Filterable Attributes.
We need to Create Mail Contacts for all Dynamic Distribution Lists in the online environment but that has not resolved the mail routing issues because Customer was not directly using the Dynamic Distribution lists & was nesting these under the Normal Distribution groups.
So when these Normal groups are synchronized with cloud, their members are null and email sent to them land no where.
Here are the mitigation steps that We have done & will be valid for majority of Customers facing the above issue:
- Alter the Dynamic Distribution lists to include Scope "Mail users with external email addresses"
This Step will include the Remote Mailboxes (mailboxes that have been moved to Exchange Online)
- Create Mail contacts for each Dynamic Distribution List in Exchange Online environment.
Both of the steps are widely known & documented on various blogs, here are the extra steps that we have performed to mitigate the issue in this particular case.
- Move the Normal Distribution groups that have nested dynamic Lists to Do Not Sync OU (Create OU that will unchecked for Sync) inside Azure Active Directory Synchronization.
- Create the Normal Distribution groups with Same Name in Exchange Online.
- ADD the Legacy Exchange DN address(extract from OnPremise DL) to Normal DL in online.
- Nest the Created Mail Contacts(Created for Dynamic Distribution lists) to the Normal Distribution List Created Online.
When above is followed -> Migrated users can use the same experience for Dynamic Distributions groups as he/She was having when account was On-premise. I will be sharing the other similar situations along with the solutions in future posts :)
Thanks for Reading
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