Dovecot LDAP/AD with exim as mta

Hi,

I have done configuration dovecot/exim/samba4ad.

I use dovecot-lda not exim to deliver mail. And dovecot to authentify users.

I have users with mail address on AD. When i sent mail to user mail address, its working.

I have distribution group or group with mail address on AD and users as member of this groups. But when i send mail to group mail address, its not working

Dovecot-lda can do it ? Or i need do it with exim (or postfix) ?

Thanks

Benoît