[Samba] LDAP schema extended samba 4.19.0

[Omnis ludis - games]

I expanded my schema and am trying to add these entries to ldap
dn: cn=test,ou=soft_users,dc=soft,dc=biz
cn: test
objectClass: nisMailAlias
objectClass: top
rfc822MailMember: test at ml.soft.com
but I get the following error
ldbadd -H /opt/samba/private/sam.ldb mail3.ldif
ERR: Naming violation : "structural objectClass nisMailAlias is not a valid
child class for OU=soft_users,DC=soft,DC=biz" on DN
cn=test,ou=soft_users,dc=soft,dc=biz
how can I fix this error and add objects to ldap?