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Stripping attachments from non-delivery reports

If you're dealing with bandwidth or disk space considerations, you can force Exchange to omit attachments in NDRs, or exclude attachments larger than a certain size.

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Non-delivery reports (NDRs) are messages automatically generated by Exchange when a particular piece of e-mail cannot reach its intended recipient. If the send operation fails, the sender receives a report that provides details about the failed message.

Any attachments associated with a failed message are typically included in an NDR. However, if you're dealing with bandwidth or disk space considerations, you can force Microsoft Exchange to omit attachments in NDRs -- or at least exclude attachments larger than a certain size.

To enforce this rule:

  1. Open the registry of the Exchange server in question and navigate to:


  2. Add a new key named Queuing (no class ID is needed).

  3. Inside Queuing, add a DWORD value named MaxDSNSize.

    This value is the maximum size of an allowed attachment (in bytes) on an NDR. You can set this to any size you feel is reasonable. For instance, if you don't want attachments over 64 K in NDRs, set this value to 65535 (decimal). The SMTP service will need to be reset for the value to take effect.

There are a couple of drawbacks to stripping attachments from NDRs. For one, you can't automatically resend any such "bounced" messages by using the Send Again option in the NDR. Removing attachments also gets rid of the details needed to resend the message as is.

On the other hand, if users retain a copy of all sent mail in Outlook or in an Exchange folder, they can always resend copies of failed messages from there.

This limit does not have an effect on NDRs generated by messages not sent by SMTP -- for example, an e-mail sent from one Exchange mailbox to another that isn't delivered properly.

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter.

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Related information from

  • Reference Center: Non-Delivery Reports (NDRs)
  • Tip: Dealing with undeliverable messages in Exchange Server

  • Dig Deeper on Exchange Server setup and troubleshooting