SMTP Status Codes
The standard protocol for sending email across the Internet. SMTP reply codes indicate the success or failure of mail transactions.
View Specification →200-299 2xx Positive Completion
The requested action has been successfully completed.
System status or help reply.
Help message. Provides information about the server commands.
The SMTP service is ready. Sent as a greeting when a connection is established.
The server is closing the transmission channel.
Authentication succeeded. The client is now authenticated.
The requested mail action was completed successfully.
User not local; the message will be forwarded.
Cannot verify the user, but will attempt delivery.
300-399 3xx Positive Intermediate
The command has been accepted but the server requires further information.
400-499 4xx Transient Negative
The command was not accepted and the action was not performed. Retry may succeed.
Service not available, closing transmission channel. The server is shutting down.
Mailbox unavailable. The action was not taken — mailbox busy or temporarily blocked.
Requested action aborted due to a local error in processing.
Requested action not taken — insufficient system storage.
Server unable to accommodate the parameters.
500-599 5xx Permanent Negative
The command was not accepted and the action was not performed. Do not retry.
Syntax error, command unrecognized. This may include command line too long.
Syntax error in parameters or arguments.
Command not implemented.
Bad sequence of commands.
Command parameter not implemented.
Host does not accept mail.
Authentication required. Must authenticate before sending mail.
Authentication credentials invalid.
Requested action not taken — mailbox unavailable or not found.
User not local; please try forwarding.
Requested mail action aborted — exceeded storage allocation.
Requested action not taken — mailbox name not allowed.
Transaction has failed. Catch-all for permanent failures.
Domain does not accept mail.