I have the problem that the title mention. I am trying to create this entry :

dn: cn=usuario2,ou=st,o=um,c=es
changetype: add
objectclass: stPerson
sn: usuario2
mobile: 657132819
correo: usuario2@st.um

using the command :

ldapmodify -D "cn=admin,o=um,c=es" -W -H ldap://ldap -f st.ldif

if i only change the objectclass to "inetOrgPerson" and the attribute "correo" to "mail", everything works well so my DIT is just fine and it's my objectclass "stPerson" that is giving me the problem.
This is my definition of the "stPerson" objectclass :

#Definición de ObjectClass "stPerson" y atributo "correo"
dn: cn=stSchema,cn=schema,cn=config
objectClass: olcSchemaConfig

olcObjectClasses: ( 1.3.6.1.4.1.4203.666.1.1 NAME 'stPerson' SUP inetOrgPerson STRUCTURAL MUST correo)
olcAttributeTypes: ( 1.3.6.1.4.1.4203.666.1.2 NAME 'correo' SUP mail)

I already added this scheme to the configuration DIT using the command :

ldapadd -Y EXTERNAL -H ldapi:/// -f stSchema.ldif

and it says :

SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
adding new entry "cn=stSchema,cn=schema,cn=config"

I do not see where is the problem.