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
...
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.
Anyone interested in specifying this?