Update 3213654 for Microsoft Outlook 2016 that was released on June 30, 2017, is not available. The fix that is described in the article is available by installing update 4011052 (Description of the security update for Outlook 2016: July 27, 2017).
This update fixes the following attachment issues that were reported after the release of the June update. For more information, see Outlook known issues in the June 2017 security updates.
If an email message includes an attached email message, and the subject line of the attached message ends with an unsafe file name extension (as listed in the Blocked attachments in Outlook Office webpage), the email attachment is blocked for recipients.
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Article ID: 3213654 - Last Review: Aug 15, 2017 - Revision: 22