[Techtalk] sendmail question

[Kai MacTane]

At 9/10/03 07:15 AM , Lena M wrote:

>I'm working on securing my sendmail. I configured so it doesn't show a
>banner containing its version numbe. I also disabled "help" feature.
>In addition, I would  like to get rid of the extra info that shows up after
>'ehlo blah-blah' command (see below)

If you do this, you'll be violating RFC2822 (see 
http://www.faqs.org/rfcs/rfc2821.html). In particular, the following bits:

3.2 Client Initiation
    Once the server has sent the welcoming message and the client has
    received it, the client normally sends the EHLO command to the
    server, indicating the client's identity.  In addition to opening the
    session, use of EHLO indicates that the client is able to process
    service extensions **and requests that the server provide a list of the
    extensions it supports.** [emphasis added]

and this part:

4.1.1.1  Extended HELLO (EHLO) or HELLO (HELO)
    ...A client SMTP SHOULD start an SMTP session by issuing the EHLO
    command.  If the SMTP server supports the SMTP service extensions it
    will give a successful response, a failure response, or an error
    response.  If the SMTP server, in violation of this specification,
    does not support any SMTP service extensions it will generate an
    error response....

    Normally, the response to EHLO will be a multiline reply.  Each line
    of the response contains a keyword and, optionally, one or more
    parameters.

Basically, the EHLO command is *supposed* to ask your server "what commands 
do you support?" The server has to respond to that.

Also, disabling the HELP command is a little iffy, as the RFC states, "SMTP 
servers SHOULD support HELP without arguments and MAY support it with 
arguments." But it's not technically violating the RFC to drop HELP.

                                                 --Kai MacTane
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