Event ID - 2051

Event Id2051
SourceMSExchangeMTA
DescriptionA fatal internal MTA error occurred. Contact Microsoft Technical Support. An illegal GET from element <name> occurred at offset <value>. [<value> <value> <value> <value>] (16)
Event InformationThe message transfer agent (MTA) may experience a performance problem when expanding extremely large distribution lists. The problem can also be triggered if the recipient name field being transferred into the MTA is larger than the buffer space available. If a failure occurred during the processing of a message, key routing information for some addresses on the recipients list may not be consistent upon restart, causing the error described above. Verify that the latest Service Pack is installed for this version of Microsoft Exchange Server.

According to Microsoft:
CAUSE:
These problems can occur when the Dbserver.sch file that is included with Microsoft Exchange Server 5.0 is installed on your hard disk, even though you have applied Exchange Server 5.0 Service Pack 1 or Service Pack 2. This can occur for either of the following reasons:
When you applied Service Pack 1 or Service Pack 2, the Dbserver.sch file was not updated.
When you applied Service Pack 1 or Service Pack 2, the Dbserver.sch file was updated properly. However, after you applied Service Pack 1 or Service Pack 2, the Dbserver.sch file was replaced with the version of the file that is included with Exchange Server 5.0.
RESOLUTION:
To work around this problem, reapply Exchange Server 5.0 Service Pack 1 or Service Pack 2. If the problem still occurs, rename the Dbserver.sch file in the Exchsrvr\Mtadata folder on your hard disk, and then use one of the following methods to obtain a new copy of the file:
Copy the Dbserver.sch file from your Service Pack 1 or Service Pack 2 (depending on the Service Pack you have applied) compact disc or disks to the Exchsrvr\Mtadata folder on your hard disk.
Decompress the self-extracting Service Pack 1 or Service Pack 2 file that you downloaded from an online service (if you have not already done so), and then copy the Dbserver.sch file from the resulting Mtadata folder to the Exchsrvr\Mtadata folder on your hard di
Reference LinksXCON: MTA Stops Unexpectedly or Stops Transferring Messages

XCON: The MTA Logs Event ID 2050 or 2051 Error Messages on a Defense Message System Server

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