REPLY CODES IN NUMERICAL ORDER
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)
535 SMTP Authentication unsuccessful/Bad username or password
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 COMMANDS
REPLY CODES GROUPED BY COMMAND
Command Code: connect
220 <domain> Service ready
421 <domain> Service not available, closing transmission channel
- This may be a reply to any command if the service knows it must shut down.
- Please refer to http://supportcenteronline.com/ics/support/default.asp?deptID=468&task=knowledge&questionID=170
Command Code: HELO
250 Requested mail action okay, completed
- Your ISP mail server have successfully executes a command and the DNS is reporting a positive delivery.
500 Syntax error, command unrecognised
- This may include errors such as command line too long.
501 Syntax error in parameters or arguments
- Indicates possible poor (noisy dialup) or an intermittent drop in network line connection that caused your mail client to send erroneous command to the mail server.
504 Command parameter not implemented
- Indicates (probable) that your ISP mail server did not recognized a command sent
521 <domain> does not accept mail [rfc1846]
- You must be pop-authenticated before you can use this SMTP server and you must use your mail address for the Sender/From field.
421 <domain> Service not available, closing transmission channel
Command Code 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
Command Code: MAIL
250 Requested mail action okay, completed
552 Requested mail action aborted: exceeded storage allocation
- ISP mail server indicates, probable overloading from too many messages.
451 Requested action aborted: local error in processing
- Your ISP mail server indicates that the mailing has been interrupted, usually due to overloading from too many messages or transient failure is one in which the message sent is valid, but some temporary event prevents the successful sending of the message. Sending in the future may be successful.
452 Requested action not taken: insufficient system storage
- Your ISP mail server indicates, probable overloading from too many messages and sending in the future may be successful.
500 Syntax error, command unrecognised
501 Syntax error in parameters or arguments
421 <domain> Service not available, closing transmission channel
Command Code: RCPT
250 Requested mail action okay, completed
251 User not local; will forward to <forward-path>
- Your message to a specified email address is not local to the mail server, but it will accept and forward the message to a different recipient email address.
550 Requested action not taken: mailbox unavailable
- Indicates that your recipient's email address was not recognized by your ISP mail server or (mailbox not found or cannot access it).
551 User not local; please try <forward-path>
- Indicates that the recipient's email address have changed and your ISP mail server is forwarding it back to you and/or your ISP SMTP mail server does not accept email when neither the sender nor the recipient is a local user--this feature was implemented to protect the mail server from being used by spammers to relay their messages by using another company’s network and computer resources.
552 Requested mail action aborted: exceeded storage allocation
553 Requested action not taken: mailbox name not allowed
- (E.g., mailbox syntax incorrect) Some mail servers have the option to reduce the number of concurrent connection and also the number of messages sent per connection. If you have a lot of messages queued up (being sent) for a domain, it could go over the maximum number of messages per connection and/or some change to the message and/or destination must be made for successful delivery.
450 Requested mail action not taken: mailbox unavailable
- Your ISP mail server indicates that an email address does not exist or the mailbox is busy. It could be the network connection went down while sending, or it could also happen if the remote mail server does not want to accept mail from your for some reason i.e. (IP address, From address, Recipient, etc.)
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
- Indicates (probable) that your ISP mail server did not recognized a command sent that is erroneous. Some temporary event prevents the successful sending of the message or an intermittent drop in network line connection that caused your mail client to send erroneous command and sending in the future may be successful.
521 <domain> does not accept mail [rfc1846]
421 <domain> Service not available, closing transmission channel
Command Code: DATA
354 Start mail input; end with <CRLF>.<CRLF>
- Indicates mail server is ready to accept the message or instruct your mail client to send the message body after the mail server has received the message headers.
451 Requested action aborted: local error in processing
554 Transaction failed
- A permanent failure is one which is not likely to be resolved by resending the message in its current form and some change to the message and/or destination must be made for successful delivery.
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
Command Code: 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
Command Code: 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
- Indicates that your ISP mail server did not recognized a command sent.
421 <domain> Service not available, closing transmission channel
Command Code: 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
Command Code: 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
Command Code: 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
Command Code: 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
Command Code: 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
Command Code: 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
Command Code: QUIT
221 <domain> Service closing transmission channel
- To stop sending email after a QUIT signal is send to your ISP mail server.
500 Syntax error, command unrecognised
Command Code: TURN
250 Requested mail action okay, completed
502 Command not implemented
500 Syntax error, command unrecognised
503 Bad sequence of commands
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UNDERSTANDING SMTP ERROR CODES
All SMTP codes consist of three digits, for example, 550, 221, 354, etc. Not all of them mean some type of error. In order to understand how these codes work, you have to know that each digit (the first, the second and the third) have there own meaning.
The first digit tells you if your command was accepted and processed. There are five different values for that:
1. Mail server has accepted the command, but does not yet take any action. A confirmation message is required.
2. Mail server has completed the task successfully without errors.
3. Mail server has understood the request, but requires further information to complete it.
4. Mail server has encountered a temporary failure. If the command is repeated without any change, it might be
completed. Try again, it may help!
5. Mail server has encountered a fatal error. Your request can't be processed.
IMPORTANT: Codes that start with 4 and 5 are the ones that tell you that your message won't be sent until you find and fix the problem.
The second digit tells you more:
0: Syntax error has occurred
1: Information reply (for example to HELP request)
2: This digit refers to the status of connection
3: Unspecified
4: Unspecified
5: This digit refers to the status of the mail server
The third (last) digit of the code tells you the details of mail transferring status. This leads us to the detailed list of ESMTP server response codes, as layed down in RFC 2821 and later extensions. Please refer to http://www.rfc-editor.org/ for details.
