Vorraussetzung: exim4 cyrus-imapd

/etc/exim4/conf.d/transport/30_exim4-config_cyrus_deliver :

cyrus_delivery:
      driver = lmtp
      socket = /var/run/cyrus/socket/lmtp
      batch_max = 20
      group = mail

/etc/exim4/update-exim4.conf.conf :

dc_localdelivery='cyrus_delivery'

update-exim4.conf
/etc/init.d/exim4 restart