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RFC 7504
Title: SMTP 521 and 556 Reply Codes
Author: J. Klensin
Status: Standards Track
Stream: IETF
Date: June 2015
Mailbox: [email protected]
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
memo is unlimited.
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