Event ID - 3020

Event Id3020
DescriptionA non-delivery report with a status code of number was generated for recipient recipient (Message-ID message id).
Event InformationCause:
A forward loop was detected by the categorizer. This is a common hosting configuration problem caused when someone uses the provisioning tool to create a contact in one organization unit and creates a user in a different organization user that share the same e-mail address.

Verify that you do not have a user in organizational unit and a contact in a different organizational unit that have the same e-mail address.

This message from newsgroup may help you:
First you should find out if you have duplicate mail addresses in your Windows Forest.
Open Active Directory Users and Computers on an computer with Exchange 2000/2003 administration tools. Do a Find, against all domains. Select Exchange Recipients from the drop down menu. From the Advanced menu select proxy addresses or Legacy DN (I don't think this is exposed). Set the proxy address to "X500:/O=FUNDS INC/OU=FIRST ADMINISTRATIVE GROUP/CN=RECIPIENTS/CN=KerrySue" see if that results in any duplicates.
You could also try to search for mailnickname = "KerrySue" or the smtp addresses of the user. basically you are trying to find out if you have two objects with the same email addresses. Once you find them resolve them correctly (remove the contact if there is a mailbox, remove the mailbox entries from the User if they shouldn't be there).
Reference LinksMicrosoft product: Exchange Version: 6.5.6940.0 Event Source: MSExchangeTransport Event ID: 3020

XADM: One Public Folder Does Not Replicate To Other Servers

Microsoft product: Exchange Version: 6.5.7638.0 Event Source: MSExchangeTransport Event ID: 3020

Event Id:3020 Source Id:MSExchangeTransport

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