Hi Murray,
At 23:27 28-10-2011, Murray S. Kucherawy wrote:
That's a pretty strong argument in favour of creating something new
rather than overloading something old. But that too runs headlong
into likely interoperability concerns. There's a bit of induced
paralysis there that needs to be overcome.
Yes.
I would say that it is more about adoption than
interoperability. There is also "domain of applicability" to
consider. It can help in addressing interoperability concerns or
even protocol "violations".
Someone else suggested nothing parses SMTP replies beyond the three
digits. That's not true in ESMTP; the enhanced status codes (if
used) and the reply to EHLO itself are structured. It's not true in
pure SMTP either, where I think some of the replies are specified
beyond the three digits (the 220 greeting, the reply to HELO, and
the 221 message, as I recall).
The keyword is "structured text".
BTW, you can even get into trouble with assumptions about the three
digits being what the specification say they should be as some
implementation diverge in their interpretation. The careful reader
will take note of the discussion about that.
John suggested a new reply code series, but that scares me a bit;
what would a staunch legacy implementation be likely to do with that?
The legacy implementation could ignore it. In practice, it may cause
code path issues if there isn't any protocol negotiation.
Regards,
-sm