[exim] feature request: new local scan return value

Hi!

I would find very useful to be able to reject and close a connection
depending on the result of a local scan action. I my setup this would
be used to close a connection after a high score spam is received, not
allowing the sender to push more messages though that connection.

To achieve this, it would be necessary to add a new return value to the
local scan function, something like

LOCAL_SCAN_REJECT_CLOSE

or

LOCAL_SCAN_CLOSE

which has the effect of closing the connection, posibly after rejecting
the message.

Regards.