> Can you tell me why the 250 is followed by a '-' on an EHLO and with a HELO
> without that?
> In: EHLO 188.8.131.52
> Out: 250-myservername.domain.com
> In: HELO reee6f7a87395a
> Out: 250 myservername.domain.com
A space after the status code means this is the last line in a multine
reply. in other lines, a '-' is used instead. in short, it goes like this:
CMD foo bar blah
Read RFC821, RFC2821, and RFC1869. If you are looking at SMTP traffic
at this level, you cannot understand what it going on adequately
without reading all three of those (and understanding them.)
The short answer: HELO is the historic introduction command in SMTP
and using it tells a MTA to stick to the RFC821 definition of SMTP.
EHLO signals the MTA that the client wants to use some extension to
the RFC821 spec, and the response to EHLO is a multi-line response
listing the extensions supported by the server.