Multiple EUQ (End User Quarantine) reports are sent to users that use aliases in Trend Micro Email Security (TMEMS). The logic of sending quarantine digest message from the Admin Console is explained here.
TMEMS will aggregated the digest report for each user based on alias address settings in directory services that are supposedly synched to TMEMS by the synch client tool, and then only send one consolidated copy to the primary address only.
For detailed information on how to use the how to use the Directory Synchronization Tool, refer to the Directory Synchronization Tool Users Guide.
The user then has to set his own primary alias by following the steps in Aliases Synchronized from Directories.
The above link explains that if a primary alias is set, then the quarantine digest email messages will be merged into one message and sent only to the primary alias. If not, the digest messages will be distributed to each email address associated with the current end user account.
The primary alias set this way has a higher priority than those set by the Active Directory Sync Tool.