12. Normative References

[ESMTP] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. Crocker, "SMTP Service Extensions", STD 10, RFC 1869, November 1995.

[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[SMTP-MTA] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, August 1982.

Partridge, C., "Mail routing and the domain system", STD 10, RFC 974, January 1986.

Braden, R., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, October 1989.

Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April 2001.