After upgrading mail-archives I checked the APR error messages the instance writes. Those are not new, they were also written for the odl version.
The messages are due to the fact, that the old and the new bundled apr versions are compiled without iconv support. So mod_mbox can not convert alternative charsets to utf-8. Not sure currently, which features of mod_mbox this breaks, but various encoding issues are expected. I will provide a new build including iconv support. Regards, Rainer