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SMTP 521 Reply Code

Document Type Replaced Internet-Draft (individual)
Expired & archived
Author Dr. John C. Klensin
Last updated 2014-09-17 (Latest revision 2014-08-11)
Replaced by draft-klensin-smtp-521code
RFC stream (None)
Intended RFC status (None)
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state Replaced by draft-klensin-smtp-521code
Telechat date (None)
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


This memo defines a new Simple Mail Transfer Protocol (SMTP) reply code, 521, which one may use to indicate that an Internet host does not accept incoming mail. It is a standards track replacement for the earlier, experimental, RFC 1846 without any substantive changes.


Dr. John C. Klensin

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)