SMTPBefehle

SMTPBefehle, also known as SMTP commands, are instructions sent from an email client to an SMTP server to control the flow of email messages. These commands are the fundamental building blocks of the Simple Mail Transfer Protocol, the standard for sending emails across the internet.

The communication between a client and server begins with the client initiating a connection. Once connected, the server responds with a 220 greeting. The client then sends its HELO or EHLO command, identifying itself to the server. EHLO, the extended HELO, is preferred as it allows the server to advertise its supported extensions.

Following identification, the client uses the MAIL FROM command to specify the sender's email address. The RCPT TO command is then used to specify each recipient's email address. For each valid recipient, the server responds with a 250 OK.

Once all recipients are listed, the client sends the DATA command to signal the beginning of the email message content. The server responds with a 354 Start mail input message. The client then sends the actual email content, including headers (like Subject, To, From) and the body, ending the message with a single period on a line by itself.

Upon receiving the period, the server processes the email and responds with a 250 OK if successful, or an error code if there was a problem. The client can then use the QUIT command to close the connection gracefully. Various other commands exist for specific functions, such as NOOP for a keep-alive or RSET to reset the current transaction. Understanding these basic SMTPBefehle is crucial for comprehending how email is sent and for troubleshooting email delivery issues.