email ESMTP SMTP data codes command groups

Request For Comment (RFC) A document outlining a standard and proposed standard to an existing standard.
The protocols and standards that currently govern RFC are constantly changing and not limited to below examples.

ESMTP/SMTP Connect and Data Receive
Reply Codes Command Groups

Command	Code	Description

Connect	220	<domain> Service ready
	421	<domain> Service not available, closing transmission channel

HELO	250	Requested mail action okay, completed
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	504	Command parameter not implemented
	521	<domain> does not accept mail [rfc1846]
	421	<domain> Service not available, closing transmission channel

EHLO	250	Requested mail action okay, completed
	550	Not implemented
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	504	Command parameter not implemented
	421	<domain> Service not available, closing transmission channel

MAIL	250	Requested mail action okay, completed
	552	Requested mail action aborted: exceeded storage allocation
	451	Requested action aborted: local error in processing

RFC defined SMTP Status Error Codes rfc 821 SMTP is a simple ASCII protocol. SMTP is a protocol governing electronic mail transmission and reception (sending and receiving emails between mail servers)

New enhanced ESMTP Status/Error Codes and descriptions defined by RFC Protocol

ESMTP Status Error Codes Command Group The protocols and standards that currently govern RFC are constantly changing

Definition of extension to the SMTP service RFC-821 Servers supporting the Enhanced-Status-Codes extension must preface the text part of almost all response lines with a status code.

Winsock Error Codes
There are two kinds of errors in Windows Sockets: task-based and socket-based.

Mail Object Error Message
If the send method of the SMTP Object is returning 0 then it means the mail server accepted the e-mail with no error message.

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	452	Requested action not taken: insufficient system storage
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	421	<domain> Service not available, closing transmission channel

RCPT	250	Requested mail action okay, completed
	251	User not local; will forward to <forward-path>
	550	Requested action not taken: mailbox unavailable
	551	User not local; please try <forward-path>
	552	Requested mail action aborted: exceeded storage allocation
	553	Requested action not taken: mailbox name not allowed
	450	Requested mail action not taken: mailbox unavailable
	451	Requested action aborted: local error in processing
	452	Requested action not taken: insufficient system storage
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	503	Bad sequence of commands
	521	<domain> does not accept mail [rfc1846]
	421	<domain> Service not available, closing transmission channel


DATA	354	Start mail input; end with <CRLF>.<CRLF>
	451	Requested action aborted: local error in processing
	554	Transaction failed
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	503	Bad sequence of commands
	421	<domain> Service not available, closing transmission channel

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ESMTP/SMTP Connect and Data Receive
Reply Codes Command Groups

Received data
Receive	250	Requested mail action okay, completed
	552	Requested mail action aborted: exceeded storage allocation
	554	Transaction failed
	451	Requested action aborted: local error in processing
	452	Requested action not taken: insufficient system storage

RSET	200	(nonstandard success response, see rfc876)
	250	Requested mail action okay, completed
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	504	Command parameter not implemented
	421	<domain> Service not available, closing transmission channel

SEND	250	Requested mail action okay, completed
	552	Requested mail action aborted: exceeded storage allocation
	451	Requested action aborted: local error in processing
	452	Requested action not taken: insufficient system storage
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	502	Command not implemented
	421	<domain> Service not available, closing transmission channel

SOML	250	Requested mail action okay, completed
	552	Requested mail action aborted: exceeded storage allocation
	451	Requested action aborted: local error in processing
	452	Requested action not taken: insufficient system storage
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	502	Command not implemented
	421	<domain> Service not available, closing transmission channel

SAML	250	Requested mail action okay, completed
	552	Requested mail action aborted: exceeded storage allocation
	451	Requested action aborted: local error in processing
	452	Requested action not taken: insufficient system storage
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	502	Command not implemented
	421	<domain> Service not available, closing transmission channel

VRFY	250	Requested mail action okay, completed
	251	User not local; will forward to <forward-path>
	550	Requested action not taken: mailbox unavailable
	551	User not local; please try <forward-path>
	553	Requested action not taken: mailbox name not allowed
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	502	Command not implemented
	504	Command parameter not implemented
	421	<domain> Service not available, closing transmission channel

EXPN	250	Requested mail action okay, completed
	550	Requested action not taken: mailbox unavailable
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	502	Command not implemented
	504	Command parameter not implemented
	421	<domain> Service not available, closing transmission channel

HELP	211	System status, or system help reply
	214	Help message
	500	Syntax error, command unrecognized
	501	Syntax error in parameters or arguments
	502	Command not implemented
	504	Command parameter not implemented
	421	<domain> Service not available, closing transmission channel

NOOP	200	(nonstandard success response, see http://www.faqs.org/rfcs/rfc876.html
	250	Requested mail action okay, completed
	500	Syntax error, command unrecognized
	421	<domain> Service not available, closing transmission channel

QUIT	221	<domain> Service closing transmission channel
	500	Syntax error, command unrecognized

TURN	250	Requested mail action okay, completed
	502	Command not implemented
	500	Syntax error, command unrecognized
	503	Bad sequence of commands