Common 'Email Log' Error Codes

After every delivery stage, a three-digit response code is sent from the mail server. The first number indicates whether the command was successful or unsuccessful; the second digit indicates the type of error; and the third provides additional information to resolve the potential problem. These codes are found in Salesforce by running an Email Log File, found in Classic: Setup > Logs > Email Log Files and in LEX: Setup > Environments > Logs > Email Log File and viewing the attached log file. This is how you can verify that an email is being sent and there is a none delivery or bounce from the intended recipient.

Each code is composed of three digits (X.X.X). The first digit gives the status of the email message:

• 2 means the email was successfully sent;
• 4 means there was a temporary problem while sending the email (your email server tries to send it again or you must resend it, depending on your server settings). Such error messages are using codes like 4.X.X, where X.X are used in order to give more precise information about the error;
• 5 means there’s a permanent or fatal error related to the email (the email address of the receiver doesn’t exist, it doesn't accept emails from you, and so on). Such error messages are using codes like 5.X.X, where X.X are used in order to give more precise information about the error.

Here are a few that you see frequently working in SFDC:

• 421 - The service is not available and the connection will be closed.
• 450 - The requested command failed because the user’s mailbox was unavailable (such as being full). Try again later.
• 451 - The command has been aborted due to a server error (on their side).
• 452 - The command has been aborted because the server has insufficient system storage.
• 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 (such as not found).
• 551 - The recipient is not local to the server.
• 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 for some unstated reason.

Here’s a complete list of email delivery error codes, based on the Extended SMTP (ESMTP) standards, where X can be 4 or 5, depending on the error type (Persistent Transient or Permanent):

• X.1.0 Other address status
• X.1.1 Bad destination mailbox address
• X.2.0 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 problem
• 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.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

See Also
Request an Email Log
Email Log Reference 
Mail Non Delivery (NDR) codes