Ldap dict for shared mailboxes

[Kees van Vloten]

Hi everybody,

I am trying to construct a LDAP dict for shared mailboxes.

There is a lot of documentation available but nothing specific to this 
usecase. I could not find anything useful on Google nor in the 
mailinglist archives :-(

The best start point seems to be the doc on shared mailbox dictionaries 
(https://doc.dovecot.org/configuration_manual/shared_mailboxes/shared_mailboxes/#user-shared-mailboxes-shared-mailbox-listing), 
in particular the example for SQL dict. But obviously LDAP is different 
than SQL. The dictionaries page 
(https://doc.dovecot.org/configuration_manual/dict/) has  LDAP example 
but it looks like it does not contain all the bit and pieces I need.

Following the structure of the SQL example, I come to something like this:

map {
   pattern = shared/shared-boxes/user/$to/$from
   base_dn = ou=shared mailboxes,dc=example,dc=com
   filter = (&(objectClass=group)(mail=%{from})

   fields {
     from_user=$from
     to_user=$to
   }
}

The "to_user" / "$to" should be filled with the 'uid' or 'email' of a 
nested group lookup of the 'member' fields of the group.

What are the mechanics to get that done? Does anyone has an example or 
pointer to documentation or is a LDAP dict for shared-mailboxes not 
possible / supported? And in the latter case, suggestions about possible 
alternatives are welcome :-)

FYI. the LDAP implementation I am using is a recent Samba4 ad-dc.

- Kees.