On Apr 4, 2007, at 4:25 PM, Gary Kline wrote:

        What I got caught on was "client," altho from the context,
        here ``client'' seems to mean the mail-server-sending-spam.'
        In the unix world, my server is the client--unless the
        client-server model is different with email.

Your mail server is constantly listening on port 25. When some other process (typically on some other host) connects to the service you are running on port 25, then the thing making the connection is the client. Even if it is a full blown MTA.

Likewise when your mail server wants to pass mail on to some other server your server initiates a connection with a destination port (typically) of 25. During that activity your MTA is acting as a client.

For mail the terms client and server have the usual unix meaning, it's just that most things that act as SMTP servers (sendmail, postfix, etc, etc) also act as SMTP clients. But note that this isn't the case the other way around. Many things that act as SMTP clients (pine, mutt, thunderbird, Outhouse) do NOT act as SMTP servers.

I guess what might be confusing here is that it is typically to client that sends the most information during an SMTP session. With HTTP it is the other way around. But think instead of doing uploading with FTP. The client sends most of the information.

I hope this helps.


Jeffrey Goldberg                        http://www.goldmark.org/jeff/

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