hi rich,
thank you for your reply.
i deleted my thunderbird-14 manually twice,
and installed (download only) the thunderbird.tcz from the ftp.nluug.nl with the info-file version thunderbird 15.0,
rebooted and could verify that there is still thunderbird-14 labeled as version 15 in the rep.
at least in ftp.nluug.nl the package is different to its info-file.
thank you for your help.