SMTP and ESMTP error code list
It is important to figure out why your email bounces. If you receive an email bounce, you can look in the bounce message to find the proper error code that will give you the reason for the bounce. Below is a list of the Standard SMTP error codes and the Extended SMTP (ESMTP) error codes.
SMTP Error Codes
This list of codes is the standard SMTP error codes you will find in most email bounces.
- 211 - System status / system help reply
- 214 - Help message
- 220 - Domain service ready
- 221 - Domain service closing transmission channel
- 250 - Requested mail action completed and OK
- 251 - Not Local User, forward email to forward path
- 252 - Cannot Verify user, will attempt delivery later
- 253 - Pending messages for node started
- 354 - Start mail input; end with .
- 355 - Octet-offset is the transaction offset
- 421 - Domain service not available, closing transmission channel
- 432 - Domain service not available, closing transmission channel
- 450 - Requested mail action not taken: mailbox unavailable. request refused
- 451 - Requested action aborted: local error in processing Request is unable to be processed, try again
- 452 - Requested action not taken: insufficient system storage
- 453 - No mail
- 454 - TLS not available due to temporary reason. Encryption required for requested authentication mechanism
- 458 - Unable to queue messages for node
- 459 - Node not allowed: reason
- 500 - Syntax error, command unrecognized
- 501 - Syntax error in parameters or arguments
- 502 - Command not implemented
- 503 - Bad sequence of commands
- 504 - Command parameter not implemented
- 510 - Check the recipient address
- 512 - Domain can not be found. Unknown host.
- 515 - Destination mailbox address invalid
- 517 - Problem with senders mail attribute, check properties
- 521 - Domain does not accept mail
- 522 - Recipient has exceeded mailbox limit
- 523 - Server limit exceeded. Message too large
- 530 - Access Denied. Authentication required
- 531 - Mail system Full
- 533 - Remote server has insufficient disk space to hold email
- 534 - Authentication mechanism is too weak. Message too big
- 535 - Multiple servers using same IP. Required Authentication
- 538 - Encryption required for requested authentication mechanism
- 540 - Email address has no DNS Server
- 541 - No response from host
- 542 - Bad Connection
- 543 - Routing server failure. No available route
- 546 - Email looping
- 547 - Delivery time-out
- 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
Extended SMTP (ESMTP) standards
The Extended SMTP error codes work in 3 digit combinations. For example, 5.2.1 is a Permanent Error where the receiving email is not accepting messages. The first number is the email message status. The second 2 numbers pinpoint the exact information bout the error.
- 2 Successfully sent the email;
- 4 Temporary problem when sending the email. The email server typically will try to send it again till it reaches retry timeout.
- 5 Permanent or Fatal error. This can be caused by a non existent email address, DNS problem, or your email was blocked by the receiving server.
Below is a list of the Extended SMTP error codes.
Note! X can be a 4 or a 5 depending on is its Temporary or Permanent.
- X.1.0 - Other address status
- X.1.1 - Bad destination mailbox address
- X.1.2 - Bad destination system address
- X.1.3 - Bad destination mailbox address syntax
- X.1.4 - Destination mailbox address ambiguous
- X.1.5 - Destination mailbox address valid
- X.1.6 - Mailbox has moved
- X.1.7 - Bad sender's mailbox address syntax
- X.1.8 - Bad sender's system address
- X.2.0 - Other or undefined mailbox status
- X.2.1 - Mailbox disabled, not accepting messages
- X.2.2 - Mailbox full
- X.2.3 - Message length exceeds administrative limit
- X.2.4 - Mailing list expansion issue
- X.3.0 - Other or undefined mail system status
- X.3.1 - Mail system full
- X.3.2 - System not accepting network messages
- X.3.3 - System not capable of selected features
- X.3.4 - Message too big for system
- X.3.5 - System incorrectly configured
- X.4.0 - Other or undefined network or routing status
- X.4.1 - No answer from host
- X.4.2 - Bad connection
- X.4.3 - Routing server failure
- X.4.4 - Unable to route
- X.4.5 - Network congestion
- X.4.6 - Routing loop detected
- X.4.7 - Delivery time expired
- X.5.0 - Other or undefined protocol status
- X.5.1 - Invalid command
- X.5.2 - Syntax error
- X.5.3 - Too many recipients
- X.5.4 - Invalid command arguments
- X.5.5 - Wrong protocol version
- X.6.0 - Other or undefined media error
- X.6.1 - Media not supported
- X.6.2 - Conversion required and prohibited
- X.6.3 - Conversion required but not supported
- X.6.4 - Conversion with loss performed
- X.6.5 - Conversion failed
- X.7.0 - Other or undefined security status
- X.7.1 - Delivery not authorized, message refused
- X.7.2 - Mailing list expansion prohibited
- X.7.3 - Security conversion required but not possible
- X.7.4 - Security features not supported
- X.7.5 - Cryptographic failure
- X.7.6 - Cryptographic algorithm not supported
- X.7.7 - Message integrity failure
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2014-03-22 10:14 am
Thank you. The listing helps me explain better to users.
2014-12-15 2:33 am
404 not found, its clear explanation, can't access the webmail login page
2014-12-15 12:09 pm
404 is not an SMTP error but a server error when it cannot find a page. Are you getting this error when trying to log in? If so, what is the URL you are trying to log into?
2015-07-03 12:49 pm
site 2 weeks I cann't send with smtp service of yahoo, error 200 "unknow error certificate bad; destination host name does not match in certificate, even if I use different PC
2015-07-06 3:40 pm
If you are one of our customers you will want to contact Live Support for account specific help.
2015-10-15 1:08 pm
Looking for some help with Server error: '452 too many recipients'. the list above says this is an system storage issue. I was able to send to the list before. Suggestion help.. thanks in advance
2015-10-15 3:13 pm
How many emails are you trying to send out at one time? Most servers have hard limits, ours are set to 50.
2015-10-19 9:30 am
One of my clients experiencing the same issue, was trying to send out an email to 130 recipients. is there a way of resolving this, maybe increase the limit?
2015-10-19 5:38 pm
Our shared servers are hard set to only allow 50 recipients per email. This is not a setting that can be changed at the account level.
2015-10-21 3:47 pm
Hi My name is himanshu.
please suggest me , my lan users are not able to send the mail,it shows in outbox, error says check with your ISP
But Lan users are able to send mails when i am changing the LAN public ip
2015-10-21 8:19 pm
Sorry for the problem with your outbound mail. If you are maintaining the IP address and email server for your installation, then I would highly recommend reviewing the bounce messages when your emails fail. These bounce- messages will give you the specific information you require to see WHY an emails. If it is failing due to a blacklist, then it will be indicated in the bounce along with the information on who to contact in order to be de-listed. This is what appears to be happening based on the fact that you're changing public IP addresses and then your mail starts working again. Please check out our article: Why do email servers get blacklisted.
I hope this helps to answer your question, please let us know if you require any further assistance.
2015-10-22 3:22 am
Thanks for responce.
Somebody suggested me to do create PTR, will it help
2015-10-22 10:35 am
Thank you for contacting us. Yes, creating SPF records with PTR can often help your email get delivered.
But keep in mind there are many reasons email may not be delivered, so it must be handled on a case-by-case basis.
Reveiwing your servers mail logs is the best method for troubleshooting most email issues.