This article describes how to change the default behavior in Exchange Server 2010 so that an NDR that includes a 5.1.7 status code is generated when a message is sent to an ambiguous recipient.
Note After you add this line to the Exchange Server 2010 Edgetransport.exe.config file, the new default behavior is to generate an NDR instead of deferring the message to the Submission queue.
<add key="NdrForAmbiguousRecipients" value="true" />
You can configure the Exchange Server 2010 deferral time in minutes when an ambiguous recipient exists. To configure the deferral time in minutes, set the following value:
private TimeSpan deferralTimeForAmbiguousRecipients
Article ID: 2812505 - Last Review: Feb 21, 2013 - Revision: 1