Comment 11 for bug 1215961

I see you've got the newer python3-dns installed, so that theory wasn't right. Would you please bump the log level in /etc/postfix-policyd-spf-python/policyd-spf.conf: to 5 and then attach a few (I shouldn't need many) messages worth of log output from the policy server. That should help me make sure I'm replicating your situation precisely.