Problems with schema?

["Erich Kolb" <ekolb@randbreceivables.com>]

I am having difficulties with getting openldap to accept the mail
attribute.  I have included both core.schema and misc.schema in my
slapd.conf file and it appears that all of the attributes which I would
like to use are working correctly, however the whole reason I would like
to use LDAP is for email directory services.  When I attempt to add this
attribute to a user, I receive the following:

Failed to add 'mail' attribute for
ldap://mail.mydomain.com:389/cn=ekolb, ou=infoservices,
dc=mydomain,dc=com
Root error: [LDAP: error code 65 - attribute 'mail' not allowed]

Any anyone offer any assistance with this problem?