The X.400 is a protocol that is defined by ITU-T and ISOs for information processing services in email transmission. The X.400 is applied to Europe and Canada and other countries, another email protocol (there is a simple mail transfer protocol introduced by IETF, ie SMTP). The X.400 supports binary representation, so there is no need to encrypt binary content during transmission. Compared to the text information of SMTP, people are more difficult to fake email addresses and content.
There is an immature between X.400 and STMP, but it also features a characteristic. Overall, X.400 is a more complex protocol, compared to SMTP, X.400 has the following independent features:
Send notification: Send notification is primarily used to report transmission success notifications (YES representation transmission success) and send failed notification (NO means transmission failed). Receive Notification: The receiving notification returns to the user transmitting end, and the report information is transmitted (such as receiving end reading information, etc.). In the X.400, the received and non-receiving notifications include information such as automatic forwarding, information deletion, and more. Safety features: X.400 defines the message transfer security mechanism and the "Security Tag" concept, and through the OID identification system's security tag mode, but in this protocol, the specific label mode is not introduced. Priority Terriage (Layer 3): Support for mail delivery sequences, sequentially transmitted by "important" to "important" according to the importance of mail. Delayed transmission: Determine the information transmission time. The service has not been widely used. Network conversion: such as converting from a graphic television to a plain text, or converted from a fax image (Fax images) here is a picture, you have no right to access. "The conversion process is not an improvement to the information, In addition, it does not support security features such as signature or encryption. Reliable transmission service: In the X.400, you can continue to transfer files after the transmission is interrupted.
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