David F. Skoll wrote:
The specific "keep alive" functionality still needs to widely tested.
But the proof of concept is well established. It does work and there is
no surprise from a programmability technical standpoint that it does.
It does not work, apparently, if the SMTP client is Sendmail, which
I'm told treats the 150- as an error. Sendmail is still a
sufficiently-popular SMTP client that any server using 150-
continuation lines will break on a large proportion of incoming
This RFC 821 (clone in 2821) "recommendation" in question:
In many cases the sender-SMTP then simply needs to search for
the reply code followed by <SP> at the beginning of a line, and
ignore all preceding lines. In a few cases, there is important
data for the sender in the reply "text". The sender will know
these cases from the current context
has been in place for 25 years.
For the exact reason we all know that SENDMAIL is popular I find it
rather odd that in these 25 years this would the first time it has
encountered such considerations, so by that I am beginning to doubt that
claim. I believe the devils in the details, especially since there are
many versions of SENDMAIL.
Also, I stand my engineering that most, if not all, even SENDMAIL until
shown otherwise, will reset their timers when the channel is active again.