{"draft":"draft-klensin-smtp-521code-07","doc_id":"RFC7504","title":"SMTP 521 and 556 Reply Codes","authors":["J. Klensin"],"format":["ASCII","HTML"],"page_count":"7","pub_status":"PROPOSED STANDARD","status":"PROPOSED STANDARD","source":"IETF - NON WORKING GROUP","abstract":"This memo defines two Simple Mail Transfer Protocol (SMTP) reply\r\ncodes, 521 and 556.  The 521 code was originally described in an\r\nExperimental RFC in 1995 and is in wide use, but has not previously\r\nbeen formally incorporated into SMTP.  The 556 code was created to\r\nsupport the new tests and actions specified in RFC 7505.  These codes\r\nare used to indicate that an Internet host does not accept incoming\r\nmail at all.  This specification is not applicable when the host\r\nsometimes accepts mail but may reject particular messages, or even\r\nall messages, under specific circumstances.","pub_date":"June 2015","keywords":["Reply code","Email","Server","No Mail"],"obsoletes":[],"obsoleted_by":[],"updates":["RFC1846","RFC5321"],"updated_by":[],"see_also":[],"doi":"10.17487\/RFC7504","errata_url":null}