[Dovecot] Secondary groups from ldap

Hello,

I'm trying to configure my user_attrs using LDAP as the userdb so that
dovecot knows what secondary groups a user is a member of. The LDAP
backend is an Open Directory implementation, which stores secondary
group affiliations as memberUid attributes in
cn=groupname,cn=groups,dc=dns,dc=name,dc=server.

With ldapsearch, my query would be:

ldapsearch -x -b cn=groups,dc=dns,dc=name,dc=server "(memberUid=ian)" cn

Is this possible to configure in Dovecot?

Thanks, Ian