Common SMTP errors and their meanings (4337333)

The mailserver within KACE appliance is Exim. The SMTP errors will be familiar to you if you have worked with other SMTP servers. This document refers to some of the more common errors that you will see.

SMTP Error Codes

This list of codes is the standard SMTP error codes you will find in most email bounces.

200 Codes (System Messages)

• 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

300 Codes

• 354 - Start mail input; end with .
• 355 - Octet-offset is the transaction offset

400 Codes (Temporary Failure)

• 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 Codes (Permenant and Fatal Errors)

• 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