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OOF Auto Reply "Loops" when addressed to internal invalid recipients

Posted on 2013-11-28
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586 Views
Last Modified: 2013-12-15
Environment:
Server 2003 R2 Standard SP2
Exchange 2003 Enterprise

We have a problem with out of office messages continuously sending to a null sender instead of receiving an ndr when we create an SMTP Connector

We recently added an SMTP connector to route mail through a designated smart hosts. Previously there were no SMTP Connectors configured. (I've since deleted the connector to stop the problems temporarily, but we need to enable again)

The following happens after we configure the SMTP Connector
1- A NULL (Fake/Invalid) internal sender sends an email to an internal recipient (we have many of these in our organization that send mail, generally from a service or application, however, it's also a concern for spoofing sender addresses)
2 -  If the internal recipient has their out of office enabled, it responds to the null sender


The auto response addressed to the null sender causes a continuous loop (verified through message tracker).

Message Tracker Shows:

SMTP: Store Driver: Message Submitted from Store
SMTP: Message Submitted to Advanced Queuing
SMTP: Started Message Submission to Advanced Queue
SMTP: Message Submitted to Categorizer
SMTP: Message Categorized and Queued for Routing
SMTP: Message Queued for Local Delivery
SMTP: Message Delivered Locally to invalid address @ internal domain .com
SMTP: Store Driver Submitted Message to MTA
SMTP: Store Driver: Message sumitted from Store
SMTP: Message Submitted to Advanced Queuing
SMTP: Started Message Submission to Advanced Queue
SMTP: Message Submitted to Categorizer
SMTP: Message Categorized and Queued for Routing
SMTP: Message Queued for Local Delivery
SMTP: Message Delivered Locally to invalid address @ internaldomain .com

** The above "loop" repeats approximately 6 times per minute.


Problems:
-There is no NDR generated
- The transaction log grows at an exponential rate as more and more "loops are created by users who have their out of office enabled and begin auto replying to the null senders.
- Additional CPU, memory and swap space is consumed.
- After a period of time, the mailstore dismounts for unknown cause - possibly due to file space, memory resources unavailable, cpu unavailable...


Temporary Resolution:
When the connector is deleted, the message sender immediately receives an NDR that the message was unable to be delivered and the "loop" stops.
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Question by:siskinds
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3 Comments
 
LVL 63

Expert Comment

by:Simon Butler (Sembee)
ID: 39683988
The SMTP Connector doesn't actually do the delivery on Exchange 2003. It is more like a sign post. Therefore the problem is most likely with the smart host not accepting the message and sending it back.

The only other option I can think of is that you have some kind of catch all in place, which is stopping the system from working correctly. Do you have recipient filtering enabled on the SMTP virtual server?

Simon.
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Author Comment

by:siskinds
ID: 39684031
Thank you for your reply.
I was able to verify earlier today that the problem exists both with and without recipient filtering enabled.
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LVL 63

Accepted Solution

by:
Simon Butler (Sembee) earned 250 total points
ID: 39688370
Back to my first thought then - the problem is with the smart host refusing to accept the message. Poor system design - but many people block the messages without a sender (against the RFC to do so) because they suspect it is spam.

Simon.
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