Mimecast for Outlook: Searching in a Folder Returns Unexpected Results

Document created by user.oxriBaJeN4 Employee on Sep 4, 2015Last modified by user.oxriBaJeN4 Employee on Oct 25, 2016
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Mimecast is aware of an isolated scenario where limiting a search to a specific folder does not return the expected results, compared to browsing the same archive folder.


Applies to


  • End user of Mimecast for Outlook




This is caused by differences in the Internet Message ID property on the transmitted archive message, and the matching replicated Archive Folders message from the Exchange mailbox.



Archive Message Index Versus Archive Folders


To understand this issue, you need to understand how message content and message folder locations are stored in the Mimecast archive:

  • Your organization's messages are archived and indexed as they are sent or received by the Mimecast Gateway.
  • The Archive Folders are updated based on folder and message metadata extracted from user mailboxes by the Advanced Mailbox Replication feature.
  • The folder and message metadata are stored in a separate location to the archive email index in the Mimecast archive.
  • Mimecast uses a proprietary calculated property to identify messages in both the archive index and the Archive Folders metadata storage.
  • The Internet Message ID is one of the values used to calculate this Mimecast property.


Searching a Folder


When a user requests a search in a specific folder, Mimecast queries your organisation's message content index. It then uses the proprietary calculated property described above to determine if each of the messages in the result set from the query can belongs in the user defined folder.

  • If the value of the calculated property is found in the specified folder, the message is returned to the user.
  • If not found, the message is omitted from the result set and not returned to the user.


Behavior Where There's an Internet Message ID Mismatch


Where the Internet Message ID in the content index is different from the corresponding message in the Archive Folders replicated from the Exchange mailbox, the Mimecast calculated property will be different. Therefore:

  • The search in folder feature will not include the messages in search results.
  • The root cause of this mismatch is outside of Mimecast's control.
  • It has been observed that this typically effects Sent Items, sent from an Microsoft Outlook client in cached mode.




There is no resolution for this scenario, it is a limitation of the way the search in a folder feature works. However, there are alternative ways for users to find such messages;

  • Use archive search without specifying a folder. This method will return all messages matching the users search criteria regardless of location, and is not effected by a mismatch of the Internet Message ID property.
  • Use the Archive Folders view to browse for messages not returned by search in a folder. This method will return all messages replicated from the Exchange mailbox regardless of a mismatch in Internet Message ID.