This is a request for a very minor change to the semantics of the PREPEND <text> result that can be returned from policy servers and/or from specific entries within an access(5) lookup table.
It would be maximally convenient if the subject <text> could be interpolated in the following trivial way: Any literal "\n" (backslash-n) sequence withing <text> is replaced with an actual newline character. This trivial change would allow prepending of multiple headers to the current e-mail message. This capability would be useful in the context of systems that tag incoming messages for later analysis and/or special processing by tools external to the mail server. Alternatively, given that the Postfix policy server protocol theoretically allows for the possibility of a policy server yielding multiple "action=PREPEND <text>" results in response to any given single request (from Postfix), it would be Nice if Postfix would in fact accept a sequence of multiple such responses from a policy server in response to a single request.