After installing and running the Trend Micro Email Security (TMEMS) Directory Synchronization Tool, it will collect 3 files/items to be used for recipient filter, group based policy management, and email aliases.

Below are the 3 items collected by the Directory Synchronization Tool and what they are used for:

• Valid Recipients
  Synchronizing valid recipients enables the Trend Micro Email Security server to verify each email message by performing a valid recipient check before the email reaches the customers inbound server.
• Groups
  Synchronizing user groups enables you to define policies for user groups in Trend Micro Email Security.
   

  OU sync is not supported, but for customers who using the Azure AD, the Dynamic Group of Azure can help this. Please refer to Dynamic membership rules for groups in Azure Active Directory.

   
• Email Aliases
  Synchronizing email aliases enables Trend Micro Email Security to identify and correlate different email addresses that belong to the same user, which facilitates the management of quarantined email messages, approved and blocked senders and integration of digest email messages for multiple end user email addresses.