Subject: RFC 7504 on SMTP 521 and 556 Reply Codes

From: [email-masked]
Date: Tue, 30 Jun 2015 16:32:56 -0700 (PDT)

A new Request for Comments is now available in online RFC libraries.

        RFC 7504

        Title:      SMTP 521 and 556 Reply Codes 
        Author:     J. Klensin
        Status:     Standards Track
        Stream:     IETF
        Date:       June 2015
        Mailbox:    [email-masked]
        Pages:      7
        Characters: 13936
        Updates:    RFC 1846, RFC 5321

        I-D Tag:    draft-klensin-smtp-521code-07.txt

        URL:        https://www.rfc-editor.org/info/rfc7504

        DOI:        http://dx.doi.org/10.17487/RFC7504

This memo defines two Simple Mail Transfer Protocol (SMTP) reply
codes, 521 and 556.  The 521 code was originally described in an
Experimental RFC in 1995 and is in wide use, but has not previously
been formally incorporated into SMTP.  The 556 code was created to
support the new tests and actions specified in RFC 7505.  These codes
are used to indicate that an Internet host does not accept incoming
mail at all.  This specification is not applicable when the host
sometimes accepts mail but may reject particular messages, or even
all messages, under specific circumstances.

This is now a Proposed Standard.

STANDARDS TRACK: This document specifies an Internet Standards Track
protocol for the Internet community, and requests discussion and suggestions
for improvements.  Please refer to the current edition of the Official
Internet Protocol Standards (https://www.rfc-editor.org/standards) for the 
standardization state and status of this protocol.  Distribution of this 
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