What error code indicates a successful SMTP transaction?

The correct answer, which indicates a successful SMTP transaction, is 250. In the context of the SMTP (Simple Mail Transfer Protocol), a status code of 250 means that the requested action has been completed successfully. This is commonly used to confirm successful delivery of an email message or that a command has been successfully executed.

Understanding the significance of the 250 response is crucial in SMTP communications, as it provides assurance to the sender or client that the server has processed their request correctly and without error. For instance, if a client sends a command to send an email, receiving a 250 response indicates that the email has been accepted and processed.

In contrast, error codes such as 404 indicate that a resource was not found, 200 typically corresponds to HTTP transactions denoting success, and 500 indicates a server error. Thus, 250 is specifically used in the SMTP context to confirm that the transaction was successful, solidifying its role as the indicator of successful operations within email processing.