3.9 Terminating Sessions and Connections
An SMTP connection is terminated when the client sends a QUIT command. The server responds with a positive reply code, after which it closes the connection.
An SMTP server MUST NOT intentionally close the connection except:
- After receiving a QUIT command and responding with a 221 reply.
- After detecting the need to shut down the SMTP service and returning a 421 response code. This response code can be issued after the server receives any command or, if necessary, asynchronously from command receipt (on the assumption that the client will receive it after the next command is issued).
In particular, a server that closes connections in response to commands that are not understood is in violation of this specification. Servers are expected to be tolerant of unknown commands, issuing a 500 reply and awaiting further instructions from the client.
An SMTP server which is forcibly shut down via external means SHOULD attempt to send a line containing a 421 response code to the SMTP client before exiting. The SMTP client will normally read the 421 response code after sending its next command.
SMTP clients that experience a connection close, reset, or other communications failure due to circumstances not under their control (in violation of the intent of this specification but sometimes unavoidable) SHOULD, to maintain the robustness of the mail system, treat the mail transaction as if a 451 response had been received and act accordingly.
Ibiltari <[EMAIL PROTECTED]> wrote:
I'm trying to fine tune my mail system, and looking at how
qmail-smtpd/vchkpw handle rejected mail i started thinking; why
qmail-smtp doesn't disconnect after the intrusion threshold? it keeps
rejecting messages (from the spammer normally) and eating cpu and band
whit. Perhaps there is a good reason to don't disconnect but i think
it could be a nice feature too.
any opinion about this?