Qmail-ldap password length

Hi all ,

I'm running qmail-ldap on slackware 12.0 .
Everything is running fine but now i found out that passwords which have
more
then 8 characters are only checked up to eight characters .
( tested with SMTP Authentification )

Example :
-----------
User : test
Password : 1234567890

User is able to login with password 12345678 or 12345678dasx324 or
12345678u and so on .

Is the password lenght a compile time option or a systemrestrication ?

Kind regards
Stefan