title: openldap add mail attribute to users
body: <p>I'm trying to add 'mail' attribute to users on my openldap server but somehow it fails. 
  I tried using ldapmodify but I get this:</p>
  
  <pre><code>ldap_modify: Object class violation (65)
  additional info: attribute 'mail' not allowed
  </code></pre>
  
  <p>Here's how my schema looks like:</p>
  
  <pre><code># LDIF Export for ou=users,dc=mydomain,dc=com
  # Server:  (ldap.mydomain.com)
  # Search Scope: sub
  # Search Filter: (objectClass=*)
  # Total Entries: 63
  
  version: 1
  
  # Entry 1: ou=users,dc=mydomain,dc=com
  dn: ou=users,dc=mydomain,dc=com
  objectclass: organizationalUnit
  objectclass: top
  ou: users
  
  # Entry 2: uid=tom.hanks,ou=users,dc=mydomain,dc=com
  dn: uid=tom.hanks,ou=users,dc=mydomain,dc=com
  cn: tom.hanks
  description: User account
  gecos: tom.hanks
  gidnumber: 100
  homedirectory: /home/tom.hanks
  loginshell: /bin/bash
  objectclass: account
  objectclass: posixAccount
  uid: tom.hanks
  uidnumber: 1005
  userpassword: blahblah
  </code></pre>