NDRs & Attachments

One of the features of Exchange 2000 that is enabled by default is that if you send a message with an attachment and your message is returned as non-deliverable, then the attachment is included in the NDR. The result is that your mailbox gets even bigger. You just know that your users never clear out their mailboxes, so your database swells even more.

In a number of Exchange systems that I've designed, I've configured the registry key that allows you to specify the maximum size a NDR can be before the attachment is stripped off. I find this a useful feature. There's one major caveat though: the users cannot use the Send Again feature on the NDR if you enable this registry key.

That being said, here's what you need to do to enable this feature:

1. Locate HKLM\System\CurrentControlSet\Services\SMTPSVC using your favourite registry editor.
2. Add a new key with the name Queuing.
3. Within the Queuing key, add MaxDSNSize as a DWORD. The value you enter is the size limit in bytes.

Restart the SMTP service for the change to take effect.

Messages larger than this size limit that generate an NDR do not return the attachment. I'll leave you to decide what a suitable size limit should be. Oh yes, and note that this registry key only applies if you're running at least Exchange 2000 SP2 - don't tell me you're running something less than SP3! I haven't personally tested this with Exchange 2003, either.

The MSKB article that references this useful information is here.