schema for `mailAlias'

[Ingvarr Zhmakin <ingvarr@mail.ru>]

Good morning.

I have my user base in LDAP. Many users have some mail aliases.
It is possible to create rfc822mailAlias objects of course but I'd
like to have some subentries in user records like:

===
dn: uid=vasya,ou=People,dc=macrohard,dc=com
uid: vasya
mailAlias: vasisualiy
mailAlias: vasechka
===

The main difficulty is how to guarantee the uniqueness of these aliases.

Some places in Internet seemed to me to show that it is possible.
Is it?

Thanks in advance.

                   Ingvarr.