Building the .cdb file for vpasswd

[qmailu]

Hi,   I am all set to migrate 350000 users to Qmail. I have created the users with dummy passwords and while injecting their original password noticed that it takes 3 hours to build the vpasswd.cdb file. After I have built the .cdb file , if I change the password for even a single user the .cdb file gets built again and worse it takes 3 hours to complete the process. The result a password change  comes into effect only after 3 hours. Can someone substantiate if this is true (hopefully it shouldn't be !!). Secondly  if I  kill the process then the whole vpasswd file gets corrupt and I seem to have lost all the passwords for the 350000 odd users. How do I solve this problem ??   My config as follows - Qmail-1.03 , vpopmail-4.9.6 and courier-imap.0.36a. My vpopmail config options were ./configure --enable-relay-clear-minutes=60 --enable-logging=y --enable-default-domain=qmailnv.maa.sify.net --enable-large-site=y --enable-roaming-users=y --enable-deliver-filter=y --enable-ip-alias-domains=y --enable-hardquota= 500000 --enable-tcpserver-file= ~vpopmail/etc/tcp.smtp while for courier-imap the options were ./configure --without-authldap --without-authmysql --without-authcram - with-authvchkpw. Would it help if I use a mysql authentication mechanism. If yes how do I proceed ? Expecting someone to crack this asap !!!! Raghu