XCON: Remote MTA Reports Syntax Error

When you connect to a remote Message Transfer Agent (MTA) via X.400 1988 conformance, the remote MTA may report a [syntax] error when it receives a P1 PDU sent from the Microsoft Exchange Server.

The element that causes the problem is the per-recipient-indicators inside the PerRecipientMessageTransferField. The Microsoft Exchange Server encodes it as an implicit BITSTRING with three unused bits in the last octet. The Recommendation X.411 Figure 4/X.411 defines that the three bits in the last octet are reserved and have the value zero.

Microsoft Exchange Server marks them as "unused," violating the size constraints.

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 4.0. This problem was corrected in Microsoft Exchange Server 4.0 U.S. Service Pack 2. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):