X.400 Email More Secure Than SMTP for EDI Messaging

The Tip of the Night for June 23, 2016 discussed emails sent in the X.400 email format, an alternative to the more familiar Simple Mail Transfer Protocol (SMTP) email addresses. These appear in this format which most litigation support analysts will have come across at some point:


John Smith <"c=US/o=Acme/ou=corp/s=Smith/g=john">


X.400 email has certain advantages that SMTP email does not.


  1. X.400 messages are in binary, whereas SMTP messages are in text format which makes the file size of SMTP messages larger.

  2. A X.400 message should never lead to an email coming in afterwards about a delivery failure. X.400 verifies the destination address is valid before the message is sent and also confirms that the total size of the message with attachments can be accepted.

  3. X.400 uses peer authentication which confirms the identity of the recipient. This can prevent email spoofing and stop junk or phishing emails which impersonate trusted sender addresses.

  4. The X.400 email protocol will also allow the author to use a back-up email address that the message can be sent to if the delivery to the original email recipient address fails.


While recent versions of Microsoft Exchange do not support X.400, EDI messages (Electronic Data Interchange) used to transmit purchase orders (see the Tip of the Night for October 25, 2018) still use the X.400 protocol. The X.400 protocol is valued for EDI messages because of the security and verification features discussed above.