pigeonhole / vacation

Hello,

we use the sieve vacation module to answer messages for certain mailboxes. vacation send back answers to most but not all messages wich is fine
and intended.

.dovecot.sieve looks like this:

require ["vacation", "variables"];

if header :matches "subject" "*" { vacation :subject "Automatic response to: ${1}" "thanks for your message"; keep; }

But now I would like to distinct messages that where answered from
those where the vacation module did not send back a message. Is it possible to store answered messages
in one folder and unanswered in an other?

# probably invalid sieve syntax if vacation .... { fileinto "answered/"; stop; else fileinto "unanswered/"; stop; }

After reading RFC 5230 I feel it's not possible at all :-/

Andreas