At 10:21 13-10-2011, Claus Assmann wrote:
It would be nice to have a standard for a server to tell a client
which restrictions it triggered, what the limits are, and what it
should do to avoid this from happening again. For example:
- number of sessions per time unit
- concurrent number of sessions
- number of transactions per session
Yes that would be nice but it is more of a local policy issue. The
above comes under connection control where the SMTP server could
provide the information to the client on a temporary error
condition. Some of the information may already be passed out as text.
It would also be helpful to have an enhanced status code that tells
a client: "don't even try one of the other MXs, it will reject you
too." That can be rather helpful for greylisting and for systems
that share traffic control information.
This one may be doable as currently the SMTP client will retry with
the next available host on a temporary error. As it would be a
significant departure from the existing SMTP specifications, it would
be better to do it through a SMTP extension.