I've installed a Debian (jessie) box with postfix and spamassassin. Configured and everything works fine.
Except receiving mails with DKIM signatur will produce a flag T_DKIM_INVALID
even if the signature is valid. See log example below.
After that, opendkim will verify the signature and let it pass.
Jan 15 14:18:21 localhost spamd[30697]: spamd: connection from localhost [127.0.0.1]:51740 to port 783, fd 5
Jan 15 14:18:21 localhost spamd[30697]: spamd: processing message <id#1234567@mail.gmail.com> for user
Jan 15 14:18:21 localhost spamd[30697]: spamd: clean message (-2.0/5.0) for user in 0.2 seconds, 2572 bytes.
Jan 15 14:18:21 localhost spamd[30697]: spamd: result: . -1 - BAYES_00,FREEMAIL_FROM,HTML_MESSAGE,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_PASS,T_DKIM_INVALID scantime=0.4,size=2553,required_score=5.0,rhost=localhost