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To ensure that messages are transferred correctly, it is important to understand how Microsoft Exchange Server implements X.400 content options. The options you use depend upon the X.400 system you connect to.
To specify content options in the X.400 Connector, you use the Advanced property page in the Microsoft Exchange Server Administrator program. When you configure for 1984 MTA conformance, text content is sent using the P2 protocol, and attachments are sent using BP 14. When you configure for 1988 MTA conformance, text content is sent using the P22 protocol, and you can configure the server to send attachments using either BP 14 or BP 15 (FTBP).
In addition to the P2 and P22 content types, Microsoft Exchange Server provides a third message content type called message database encoding format (MDBEF). MDBEF is the format used by the Microsoft Exchange Server information store. Using MDBEF with an X.400 Connector between two Microsoft Exchange Server sites provides faster throughput because messages do not have to be converted to P2/22 and then back to MDBEF. To send messages using MDBEF content, select the Allow Microsoft Exchange contents check box under X.400 link options in the X.400 Advanced property page. The Microsoft Exchange Server computers must be replicated to transmit messages in MDBEF format.
Messages that contain MAPI properties, such as rich text formatting and OLE attachments, are encapsulated using the transport-neutral encapsulation format (TNEF) and sent as an X.400 attachment. If the receiving system can process the TNEF attachment, the message is displayed with the rich text formatting or icon representation. If the receiving system cannot process TNEF or MAPI attachments, the message text and attachments may not be readable.
The Microsoft Exchange Server MTA is capable of relaying messages from a 1988 X.400 link to a 1984 X.400 link and vice versa. However, when the Microsoft Exchange Server MTA relays a 1988 body part that is not supported by a 1984 X.400 system, the message content appears blank on the receiving system. For example, ISO 8859-1 is a 1988 body part that is not supported on a 1984 link. The Microsoft Exchange Server relay MTA is connected to a system on the 1988 link that supports ISO 8859-1 and to a system on the 1984 link that supports IA5. The Microsoft Exchange Server relay MTA cannot convert ISO 8859-1 to a supported 1984 body part such as IA5. You can use the Convert incoming messages to MS Exchange contents option in the relay MTA General property page to convert the content to MDBEF. The content can then be converted to the P2 format of the receiving system connected by the 1984 link.