XCON: MTA Outbound Connection Refused by X.400 Host

• Microsoft Exchange Server, version 4.0

SYMPTOMS

Outbound connections from Microsoft Exchange Server are refused by the destination Message Transfer Agent (MTA) using X.400.

CAUSE

The reserved byte in the RFC1006 TPKT header is not necessarily 0x0 in the Microsoft Exchange MTA. This can cause connection attempts to remote MTAs to fail if the remote RFC1006 implementation requires this byte to be 0x0.

This byte is not specified to be a particular value according to RFC1006.

MORE INFORMATION

A trace of the faulting connection might yield a packet similar to the following. The line of interest in this particular situation is ISO: Reserved = 0 (0x0). The following sample shows the Reserved field with the new behavior, specifically the Reserved field will always be explicitly set to 0x0. If this field shows this to be any other value, this may be the cause of the connection failure and is corrected in SP3.

<SOURCE MACHINE> <DESTINATION MACHINE> TPDU Type: Connection Request, Len:
14 199.199.199.199 200.200.200.200 IP

FRAME: Base frame properties
ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
IP: ID = 0xC6B5; Proto = TCP; Len: 58
TCP: .AP..., len:   18, seq:  93150219-93150236, ack: 508652377, win: 8760,
src: 2185  dst:  102
ISO: RFC 1006 ISO Packet, ver: 3, Len: 4
    ISO: Version = 3 (0x3)
    ISO: Reserved = 0 (0x0)<===== RIGHT HERE
    ISO: Length = 18 (0x12)
    ISO: Data: Number of data bytes remaining = 14 (0x000E)
TPDU: Type: Connection Request, Len: 14 

STATUS

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

S E R V P A C K

Additional query words:

Keywords : kb3rdparty kbnetwork kbbug4.00 kbfix4.00.sp3 XCON
Version : winnt:4.0
Platform : winnt
Issue type :