Distribution list members from external directory

[freebsdboy]

I'm looking for the best solution to hold our external contact information so that:
1) it can be programmaticly added to/remove entries/update entries. (Because the contacts are managed in a separate SQL database system)
2) We can create distribution lists with both members from this contact list and zimbra users.
3) names/addresses in this contacts is available to zimbra users via webmail and outlook in the address book view.

I've seen mention of external LDAP directories, and this is how authentication is setup now, but no mention of internal distribution lists using external data sources. I understand we can NOT have a distribution list stored in the external LDAP.

Also seen mention of internal or shared contacts but that model seems to have the contacts data managed there and not in an external system.

Advice? Directions?

Thanks