Delivery of emails with picture attachments is delayed in Exchange Server 2016

Applies to: Exchange Server 2016 Enterprise EditionExchange Server 2016 Standard Edition


When you send an email with a picture attachment to a large distribution list (contact group) in an Exchange Server 2016 environment, you may experience a significant delay in delivery of the message.


This issue occurs because Exchange Server 2016 uses the Windows Imaging Component (WIC) to create thumbnails for picture attachments.


To work around this issue, follow these steps to disable thumbnail creation.

Note After you follow these steps, you must restart the Microsoft Exchange Mailbox Transport Delivery service to enable the workaround.

Important Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.
  1. Start Registry Editor:
    • In Windows Server 2016, select Start > Search, enter regedit in the Search box, and then select regedit.exe in the search results.
    • In Windows Server 2012, point to the upper-right corner, select Search, enter regedit in the search box, and then select regedit.exe in the search result.
    • In Windows Server 2008, select Start, enter regedit in the Search programs and files box, and then select regedit.exe in the search results.
  2. Locate and select the following subkey:

  3. On the Edit menu, point to New, and then click DWORD Value.
  4. Enter DisableThumbnailGeneration, and then press Enter.
  5. In the Details pane, select and hold (or right-click) DisableThumbnailGeneration, and then click Modify.
  6. In the Value data box, enter 1, and then click OK.
  7. Exit Registry Editor.