RFC 780 (rfc780) - Page 2 of 43
Mail Transfer Protocol
Alternative Format: Original Text Document
May 1981 RFC 780
Mail Transfer Protocol
2. THE MTP MODEL
The MTP design is based on the following model of communication: at
the initiation of the user, the sender-MTP establishes the
full-duplex transmission channel. MTP commands are generated by the
sender-MTP and sent to the receiver-MTP. MTP replies are sent from
the receiver-MTP to the sender-MTP in response to the commands.
In the simplest case, once the transmission channel is established
the MTP-sender sends a MAIL command indicating the sender and
receiver of the mail. If the MTP-receiver can accept the mail it
responds with a go ahead reply. Then the MTP-sender sends the mail
data, terminating with a special sequence. If the MTP-receiver
successfully processes the mail it responds with an OK reply.
-------------------------------------------------------------
+----------+ +----------+
+------+ | | | |
| User || | MTP | |
+------+ | Sender- |Commands/Replies| Receiver-|
+------+ | MTP || MTP | +------+
| File || | and Mail | || File |
|System| | | | | |System|
+------+ +----------+ +----------+ +------+
Sender-MTP Receiver-MTP
Model for MTP Use
Figure 1
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The MTP provides mechanisms for the transmission of mail; directly
from the sending user's host to the receiving user's host when the
two host are connected to the same transport service, or via one or
more relay MTP-servers when the source and destination hosts are not
connected to the same transport service.
To be able to provide the relay capability the MTP-server must be
supplied with the name of the ultimate destination host as well as
the destination mailbox name.
