|Component:||Microsoft Exchange Message Transfer Agent|
|Message:||An internal MTA error occurred. A NULL constant was called during an ASN.1 decode. Contact Microsoft Technical Support. [<value> <value> <value> <value>] (14)|
ASN.1 is an ISO/ITU data encoding standard that refers to Specification of Basic Encoding Rules for Abstract Syntax Notation One. The fully encoded ASN.1 envelope is in the Microsoft Exchange Server Application Protocol Data Unit (APDU) logs, which are binary representations of communication among message transfer agents (MTAs) in different sites, and between MTA and client applications within a site. APDU logs are enabled when the logging levels of the X.400 service and APDU categories are both set to Medium or greater after you select MSExchangeMTA on the Diagnostics Logging tab of the Server Properties dialog box. To create Bf*.log files, set the logging level of the APDU and X.400 categories to Maximum. These text logs are stored in the Mtadata directory. The current log is always named Bf0.log. Prior logs are named Bfx.log, where x increases as the age of the log increases.
View the bad data in the APDU log in Mtadata\Bf0.log. Reload the ASN.1 template files from the Exchange server installation compact disc. For more information, see Microsoft Knowledge Base articles 168906 and 163032.