Simple Mail Transfer Protocol
Simple Mail Transfer Protocol (SMTP) is a TCP/IP protocol used in sending and receiving e-mail. It is typically used with POP3 or Internet Message Access Protocol to save messages in a server mailbox and download them periodically from the server for the user.
SMTP commands
The following table describes the SMTP commands, the command functions, and whether the i5/OS SMTP server supports the commands.
| SMTP command | What it does | System i® supported |
|---|---|---|
| AUTH (Authentication) | Indicate an authentication mechanism to the SMTP server. Both PLAIN and LOGIN are supported. | Yes |
| DATA (Data) | Consider the lines following the command to be e-mail from the sender. | Yes |
| EHLO (Extension Hello) | Enable SMTP extensions. | Yes |
| EXPN (Expand) | Ask the receiver to confirm that a mailing list has been identified. | No |
| HELO (Hello) | Identify the SMTP sender to the SMTP receiver. | Yes |
| HELP (Help) | Ask the receiver to send helpful information to the sender. | Yes |
| MAIL (Mail) | Start an e-mail transaction to deliver the e-mail to one or more recipients. | Yes |
| NOOP (Noop) | Ask the receiver to send a valid reply (but specify no other action). | Yes |
| QUIT (Quit) | Ask the receiver to send a valid reply, and then close the transmission channel. | Yes |
| RCPT (Recipient) | Identify an individual recipient of e-mail. | Yes |
| RSET (Reset) | End the current e-mail transaction. | Yes |
| SAML (Send and mail) | Deliver e-mail to one or more workstations and recipients if the user is not active. | No |
| SEND (Send) | Deliver e-mail to one or more workstations. | No |
| SOML (Send or mail) | Deliver e-mail to one or more workstations or recipients if the user is not active. | No |
| STARTTLS (Start Transport Layer Security) | Ask the SMTP server to start Secure Sockets Layer (SSL) or TLS negotiation with the SMTP client to establish an SSL or a TLS session. | Yes |
| TURN (Turn) | Ask the receiver to send a valid reply and then become the SMTP sender, or else ask the receiver to send a refusal reply and remain the SMTP receiver. | No |
| VRFY (Verify) | Ask the receiver to confirm that a user has been identified. | Yes |