Event ID - 270

Event Id270
DescriptionA permanent error has occurred with Entity /O=ORG/OU=CORP/CN=CONFIGURATION/CN=SERVERS/CN=ServerName/CN=MICROSOFT PRIVATE MDB. Entity is a Message Object is a Normal Priority Message. Object: #######. Message ID: C=US;A= ;P=ORG;L=ServerName-########z-##### Content length:####
Event InformationExchange 5.5: If a public folder has an SMTP e-mail address, and a user who does not have rights to post to that folder sends an e-mail message to that SMTP e-mail address, Event ID 270 and Event ID 290 may be logged in the application event log of the server. A descriptive non-delivery report (NDR) may also be generated.
This issue may also occur if a user from the Internet sends an e-mail message to the public folder, and in the client permissions for that folder, the Default item under Name has anything less than Contributor permissions selected under Role. In this case, the NDR is non-descriptive. 
MSExchange 2000: In a mixed Exchange 2000 Server and Microsoft Exchange Server version 5.5 environment, if an Exchange 2000 user attempts to send mail to an Exchange Server 5.5 mail-enabled public folder, the message may not be delivered to the public folder and a non-delivery report (NDR) may be generated. Microsoft has confirmed that this is a problem in Microsoft Exchange 2000 Server. This problem was first corrected in Microsoft Exchange 2000 Server Service Pack 1. 
Fore more information about this event go through the links provided below to Microsoft articles.
Reference Links Event IDs 290 and 270 Logged Because of Public Folder Permissions

Messages Sent by Exchange 2000 Users to an Exchange Server 5.5 Mail-Enabled Public Folder May Generate an NDR

NDR When You Attempt to Send E-Mail to a Public Folder in a Mixed Environment

You Receive a Non-Delivery Report When You Send Mail Over an X.400 Connection

Store Fails to Deliver Auto-Generated Messages from X.400 Service Provider

Public Folder Object Is Not Found in the Directory

Kanji Outlook MS Mail Users Receive NDRs Sending to Exchange

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