SMTP Reply Codes

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Article ID: 156716

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Updated On:

Products

Mail Security for Domino Mail Security for Microsoft Exchange

Issue/Introduction

Overview of the SMTP protocol reply codes

Cause


Resolution

 

The SMTP status codes consists of three numbers:

The first generally tells whether the server accepted the command and if it could handle it. The five possible values are:

·         1: The server has accepted the command, but does not yet take action. A confirmation message is required. Currently, this is not used.

·         2: The server has completed the task successfully.

·         3: The server has understood the request, but requires further information to complete it.

·         4: The server has encountered a temporary failure. If the command is repeated without any change, it might be completed. Mail servers can use such temporary failures to keep untrusted senders at bay.

·         5: The server has encountered an error.

The second number gives more information. Its six possible values are:

·         0: A syntax error has occurred.

·         1: Indicates a informational reply, for example to a HELP request.

·         2: Refers to the connection status.

·         3 and 4 are unspecified.

·         5: Refers to the status of the mail system as a whole and the mail server in particular.

The last number is even more specific and shows more graduations of the mail transfer status. This leads us to the detailed list of ESMTP server response codes, as laid down in RFC 821 and later extensions.

·         211 - A system status message.

·         214 - A help message for a human reader follows.

·         220 - SMTP Service ready.

·         221 - Service closing.

·         250 - Requested action taken and completed. The best message of them all.

·         251 - The recipient is not local to the server, but the server will accept and forward the message.

·         252 - The recipient cannot be VRFYed, but the server accepts the message and attempts delivery.

·         354 - Start message input and end with <CRLF>.<CRLF>. This indicates that the server is ready to accept the message itself (after you have told it who it is from and where you want to to go).

·         421 - The service is not available and the connection will be closed.

·         450 - The requested command failed because the user's mailbox was unavailable (for example because it was locked). Try again later.

·         451 - The command has been aborted due to a server error. Not your fault. Maybe let the admin know.

·         452 - The command has been aborted because the server has insufficient system storage.

The following error messages (500-504) usually tell you that your email client is broken. It's probably best to let the program's author know.

·         500 - The server could not recognize the command due to a syntax error.

·         501 - A syntax error was encountered in command arguments.

·         502 - This command is not implemented.

·         503 - The server has encountered a bad sequence of commands.

·         504 - A command parameter is not implemented.

·         550 - The requested command failed because the user's mailbox was unavailable (for example because it was not found, or because the command was rejected for policy reasons).

·         551 - The recipient is not local to the server. The server then gives a forward address to try.

·         552 - The action was aborted due to exceeded storage allocation.

·         553 - The command was aborted because the mailbox name is invalid.

·         554 - The transaction failed. Blame it on the weather.

 

 

The syntax of the new status codes is defined as:
 
          status-code = class "." subject "." detail
          class = "2"/"4"/"5"
          subject = 1*3digit
          detail = 1*3digit
 
 

Reply codes in numerical order

Code

Meaning

200

(nonstandard success response, see rfc876)

211

System status, or system help reply

214

Help message

220

<domain> Service ready

221

<domain> Service closing transmission channel

250

Requested mail action okay, completed

251

User not local; will forward to <forward-path>

354

Start mail input; end with <CRLF>.<CRLF>

421

<domain> Service not available, closing transmission channel

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 unrecognised

501

Syntax error in parameters or arguments

502

Command not implemented

503

Bad sequence of commands

504

Command parameter not implemented

521

<domain> does not accept mail (see rfc1846)

530

Access denied (???a Sendmailism)

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

554

Transaction failed

   

 

Reply codes grouped by command

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 unrecognised

 

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 unrecognised

 

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

 

452

Requested action not taken: insufficient system storage

 

500

Syntax error, command unrecognised

 

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 unrecognised

 

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 unrecognised

 

501

Syntax error in parameters or arguments

 

503

Bad sequence of commands

 

421

<domain> Service not available, closing transmission channel

received data

   
 

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 unrecognised

 

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 unrecognised

 

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 unrecognised

 

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 unrecognised

 

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 unrecognised

 

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 unrecognised

 

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 unrecognised

 

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 rfc876)

 

250

Requested mail action okay, completed

 

500

Syntax error, command unrecognised

 

421

<domain> Service not available, closing transmission channel

QUIT

   
 

221

<domain> Service closing transmission channel

 

500

Syntax error, command unrecognised

TURN

   
 

250

Requested mail action okay, completed

 

502

Command not implemented

 

500

Syntax error, command unrecognised

 

503

Bad sequence of commands

 

 

Applies To