The OX integration is currently lacking a dovecot capable spamrunner.
Bug has been moved to OX bugzilla: https://bugs.open-xchange.com/show_bug.cgi?id=39617
Added spamrunner script in commit 62074. All output goes to syslog (mail facility). "-v" switches on verbose logging (also to syslog).
Bug was move to OX-Bugzilla. Has already been QAed by us, not yet by OX.