When trying to add new value towards the mail attribute, which is essentially the same address just with different cases, it is prevented.
I created an user like this:
dn: uid=patrick,ou=people,dc=example,dc=org
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: shadowAccount
uid: patrick
sn: User
givenName: patrick
cn: patrick
displayName: Patrick
uidNumber: 10001
gidNumber: 5000
userPassword: {SHA}[NOPE]
gecos: Patrick
loginShell: /bin/bash
homeDirectory: /home/patrick
mail: example@googlemail.com
Then I wanted to add another mail with different casing, because according to RFC 5321 those two could be different email addresses:
dn: uid=patrick,ou=people,dc=example,dc=org
changetype: modify
add: mail
mail: Example@googlemail.com
However this fails with
ldap_modify: Type or value exists (20)
additional info: modify/add: mail: value #0 already exists
While doing the same with
dn: uid=patrick,ou=people,dc=example,dc=org
changetype: modify
add: mail
mail: Example123@googlemail.com
It works fine.
Any idea how to solve this?