Why did I receive email from the IU Mail Delivery System containing another message as an attachment?

To protect computers and data on the Indiana University network, UITS scans all inbound messages for viruses and other malware, and discards messages containing suspect content. However, not all messages can be scanned: Attachments that have been encrypted or password-protected cannot be scanned; similarly, other messages might be unscannable because they have been corrupted, or have attachments that use multiple levels of compression or archiving.

UITS does not discard these messages. Instead, the Mail Delivery System (MAILER-DAEMON@indiana.edu) intercepts the message, converts it to an attachment, and sends it to the recipient with one of the following messages:

  • Encrypted attachments: Many legitimate university and commercial senders use encrypted attachments, such as password-protected PDFs, ZIP files, or Microsoft Word or Excel documents. In these cases, the Mail Delivery System sends the following message:

    The attached message contains encrypted material, and could not be scanned for viruses by the IU Mail Delivery System. If you do not trust the sender, treat the attached message with caution.

    Do not reply to this automated message. To reply to the attached message, enter the correct address directly into the "To" field.

    For more information, see https://kb.iu.edu/d/bcow.

  • Other unscannable messages: Other messages are considered unscannable if the antivirus engine times out before the message is fully scanned, or if archive attachments are nested so deeply that they exceed the maximum scanning depth. In these cases, the Mail Delivery System sends the following message:

    The attached message could not be scanned for viruses by the IU Mail Delivery System. It might have been corrupted, or might contain insecure content. If you do not trust the sender, treat the attached message with caution.

    Do not reply to this automated message. To reply to the attached message, enter the correct address directly into the "To" field.

    For more information, see https://kb.iu.edu/d/bcow.

This is a legitimate message from IU's Mail Delivery System, which contains another message with unscannable content. However, because the original message could not be scanned for viruses, you should exercise discretion if you open the message, and avoid opening any encrypted attachments unless you know and trust the sender.

This is document bcow in the Knowledge Base.
Last modified on 2016-01-28 00:00:00.

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