XCON: MTA Generates NDRs and Message Loops (176489)

SYMPTOMS

After you restart a Microsoft Exchange Server computer that has been offline for a few hours or days, the Message Transfer Agent (MTA) may start rejecting messages, holding messages in the queues, or creating message loops. All of these symptoms contribute to degraded system performance and slow mail flow. The following error may occur:

Event ID 200
Source MSExchangeMTA
Type Warning
Category X.400 Service
Description An error occurred while ASN.1 was decoding an object (dump
reference 192). [limit exceeded on set of or sequence of 30464 2614
1spdi 192 MTA XFER-IN 15 97] Event ID 2024 Source MSExchangeIS Private
TypeError Category MTA Connections Description: Unable to access the
object manager (OM) object from the Microsoft Exchange MTA for
MH_T_ALTERNATE_RECIP_ALLOWED, MH_T_CONVERSION_LOSS_PROHIBITED, etc.

CAUSE

This behavior can occur when the MTA Open Interval time is set too low. These settings are located in a few places depending on the setup. The global setting can be found by:

Opening the Microsoft Exchange Administrator program.
Highlight and expand the Exchange Site name.
Highlight the Configuration option.
Highlight MTA Site Configuration and select File, Properties.
Select the Messaging Defaults Tab.

The Administrator may also set the MTA Open Interval time on individual X400 and Dynamic RAS connectors. The Open Interval Setting is located on each connector's Override tabs on their respective property pages.

MORE INFORMATION

The Open Interval time is used to determine how long the MTA should wait before attempting an association to another MTA. The default is 600 seconds, which should suffice in most situations. The lowest value that can be entered is 15 seconds; however, if you set the value this low, the above problem will occur if the MTA has to handle a large volume of messages (such as restarting after a maintenance period). It is recommend that this setting is never below 30 seconds on a LAN and 60 seconds on a RAS connection.