TRANSFER Installation and Management Guide

P2 Messages
The X400 Gateway
068837, Update 1 to 013198 Tandem Computers Incorporated 3–3
P2 Messages—Mail
Messages
The X.400 architecture uses a protocol called P2 to format mail messages. In
TRANSFER terms, a nonmail message is a message that is not a P2 message.
Each P2 message consists of a heading followed by a series of data blocks. The
heading contains the message originator; primary, courtesy-copy, and blind-copy
recipients; and other service information. Each body part can contain a different form
of data, such as text, voice, or FAX. Different body parts can contain different types of
data, such as binary files or 8-bit ASCII text, and messages can be nested within body
parts.
Figure 3-2 illustrates the format of a typical P2 message.
Figure 3-2. A P2 Message
Heading
Body Part
Body Part
Body Part
017
In the X.400 architecture, a UA (User Agent) generates the P2 protocol and submits the
P2 message to the MTA (Message Transfer Agent), which in turn embeds the P2
message into a P1 message for routing through the X400 network. The P2 message
thus makes up the content in a P1 message.