Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Enjoy The TCP/IP Guide? Get the complete PDF!
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)
                9  TCP/IP Electronic Mail System: Concepts and Protocols (RFC 822, MIME, SMTP, POP3, IMAP)
                     9  TCP/IP Electronic Mail Delivery Protocol: The Simple Mail Transfer Protocol (SMTP)

Previous Topic/Section
SMTP Commands
Previous Page
Pages in Current Topic/Section
12
3
4
Next Page
TCP/IP Electronic Mail Access and Retrieval Protocols and Methods
Next Topic/Section

SMTP Replies and Reply Codes
(Page 3 of 4)

Common SMTP Reply Codes

Table 255 contains a list of some of the more common SMTP reply codes taken from RFC 2821, in numerical order. For each, I have shown the “typical” reply text specified in the standard, and provided additional descriptive information where I felt it was needed.


Table 255: SMTP Reply Codes

Reply Code

Reply Text

Description

211

System status or system help reply.

 

214

<Help message…>

Used for text sent in reply to the HELP command.

220

<servername> Service ready.

Greeting message sent when TCP connection is first established to an SMTP server.

221

<servername> closing transmission channel.

Goodbye message sent in response to a QUIT message.

250

Requested mail action okay, completed

Indicates successful execution of a variety of commands.

251

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

Used when the SMTP receiver agrees to forward a message to a non-local user.

252

Cannot VRFY user, but will accept message and attempt delivery

Indicates that a server tried to verify an e-mail address, but was not able to do so completely. Usually means the address appears to be valid but it was not possible to positively ascertain this to be true.

354

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

Intermediate reply to a DATA command.

421

<servername> Service not available, closing transmission channel

Sent in response to any command when the SMTP receiver prematurely terminates the connection. A common reason for this is receipt of a local shutdown command, due for example to a hardware reboot.

450

Requested mail action not taken: mailbox unavailable

Sent when a mailbox is busy due to another process accessing it.

451

Requested action aborted: local error in processing

Local processing problem on the server.

452

Requested action not taken: insufficient system storage.

Time to clean out the server's hard disk! J

500

Syntax error, command unrecognized

Response to a bad command or one that was too long.

501

Syntax error in parameters or arguments

 

502

Command not implemented

Command is valid for SMTP in general but not supported by this particular server.

503

Bad sequence of commands

Commands were not sent in the correct order, such as sending the DATA command before the MAIL command.

504

Command parameter not implemented.

 

550

Requested action not taken: mailbox unavailable

Generic response given due to a problem with a specified mailbox. This includes trying to send mail to an invalid address, refusal to relay to a non-local mailbox and so forth.

551

User not local; please try <forward-path>

Tells the SMTP sender to try a different path; may be used to support mailbox forwarding.

552

Requested mail action aborted: exceeded storage allocation

User's mailbox is full.

553

Requested action not taken: mailbox name not allowed

Specification of an invalid mailbox address.

554

Transaction failed.

General failure of a transaction.


As mentioned before, the actual text string for each reply code is implementation-specific. While the standard specifies “dry” response text such as “Requested action completed” for a 250 message, some servers customize this code, or even give different replies to different 250 messages depending on context. Again, there are examples of this in other topics.


Previous Topic/Section
SMTP Commands
Previous Page
Pages in Current Topic/Section
12
3
4
Next Page
TCP/IP Electronic Mail Access and Retrieval Protocols and Methods
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.