--On Thursday, 29 March, 2007 13:28 +0300 Matti Aarnio
<mea+ietf-smtp(_at_)nic(_dot_)funet(_dot_)fi> wrote:
Some may have noticed a trend of rejecting emails when there
are more than some small number of messages sent over same
network connection stream ?
The RFC 821 didn't state anything explicite about it, but
indirectly permits it. As I recall, RFC 2821 does not say
anything explicite either. Could 2821bis say something ?
RFC2821 specifies, as "recipients buffer" in 4.5.3.1, that a
minimum of 100 RCPT commands must be accepted, and is quite
specific about what happens in limits are exceeded. While the
additional text is not there, the 100 recipient limit comes
straight out of 821 -- "recipients buffer" under 4.5.3.
Looks pretty explicit to me.
There is _no_ limit on number of messages sent over
established SMTP protocol connection. Those receivers that
want to limit it are expected not to loose messages from
high-volume email lists that often optimize things by
sending accumulated queue over the established connection.
This is consistent with the language of both 821 and 2821, which
strongly encourages "no limit" implementations.
Could there be some EHLO-response telling that the message
transaction count is limited at the receiving server ?
Personally, I agree with Tony Finch's suggestion: if you want
this, write it up as an extension that parallels SIZE. But be
sure that you look at the 2821 text cited above carefully and
reflect it to the degree needed in your proposal.
Since such an extension would be a change to existing practice
as documented in 2821, I believe it to be out of scope for
2821bis.
john