-rw-r----- 1 vpopmail vchkpw 39 Jan 1 2004 vpopmail.mysql
Look above, the file 'vpopmail.mysql' is not readable by "others". Which is the user you're using to run the qmail-send process? it is not the 'vpopmail' user, right?
Just 'chmod 644 vpopmail.mysql' and you fix it.