I am using postfix. is there a benefit to the group based expansion piece you speak of?  Postfix is already tied to my ldap instances for user aliases, etc.

Andrew Findlay wrote:
> Adding the mail attribute is quite simple: define an AUXILIARY object
> class that permits the attribute, add that to the group entries, and
> you can then add the mail attribute.

That's what object class 'mailboxRelatedObject' [1] is for.

[1] https://tools.ietf.org/html/draft-stroeder-mailboxrelatedobject

Ciao, Michael.