> As I understand it Postfix only allows a single line return from a
> policy server.
> e.g. this is valid:
> REJECT Because I want to\n\n
> but this is not:
> PREPEND X-MYHEADER: this is my added header\nDUNNO\n\n
As documented, the protocol takes one result.
> If that is the case I want to clarify that a PREPEND or REDIRECT reply
> will result as a DUNNO as far as later processing.
Correct. PREPEND is equivalent to DUNNO, as is WARN or any feature
that makes no final decision (unlike REJECT, OK/PERMIT).