script/method to import/create large number of mailboxes in one domain not manually

hi Till/Falko and all..

environment: ipconfig 3 on Centos 5.4 - all seem to work correctly.
(websites active and relative ftp accounts and some mailboxes in one specific domain)
...
now i have to migrate, from and old postfix (not mysql) mail server, to this ispconfig server, a large number of mailboxes (circa 1200), all those belong to one specific domain;

is there a php script or ispconfig method/utility in order to import/create in "automatic" way all mailboxes ?
i mean a sort of "import" function...
obviously, i have to recreate relative password for each user mail box, not only username;
i have all mailboxes usernames/passwords stored into a excel/access file;

if this script is not possible, i am wondering if i can achieve the above task
through phpmyadmin working directly into "dbispconfig" database..
in this case i have to populate only the "mail_user" table ? (with appropriate values)
and on "server side", i have to create some dirs/folders users containers ?

thanks in advance,
P.