[exim] sieve filter

Hello,

I am using exim4.69 as packaged on debian systems.
I recently wanted to add sieve filtering for virtual users (non-local),
but all I end up doing is messing up my conf!

I have sieve router for my virtual users:

#######################################
        ldapsieve:
          debug_print = "R: ldapsieve for $local_part@$domain"
          driver = redirect
          domains = +virtual_domains
        #  condition = ${if eq{$header_X-Spam-Flag:} {No}}
          router_home_directory = /var/mail/$domain/$local_part
          transport_home_directory = /var/mail/$domain/$local_part
          file = $home/.forward
          require_files = mail:$home/.forward
          user = mail
          no_verify
          no_expn
          check_ancestor
          allow_filter
          forbid_smtp_code = true
          directory_transport = address_directory
          file_transport = address_directory
          skip_syntax_errors
          syntax_errors_to = postmaster@$domain
#######################################

and I use the regular address_directory transport (untouched) for
delivery

my sieve filter as generated by my sieve client (rouncude managesieve
plugin + pysieved) looks like this:

#######################################
        # Sieve filter
        require ["fileinto"];
        # rule:[another]
        if anyof (true)
        {
            fileinto "Drafts";
        }
#######################################

All deliveries fails with the following error:

#######################################
FROM DEBUG -d+all
#######################################
22:43:14 30035 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
22:43:14 30035 Considering: Drafts
22:43:14 30035 unique = Drafts:lolita@???
22:43:14 30035 queued for address_directory transport
22:43:14 30035 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
22:43:14 30035 After routing:
22:43:14 30035   Local deliveries:
22:43:14 30035     Drafts
22:43:14 30035   Remote deliveries:
22:43:14 30035   Failed addresses:
22:43:14 30035   Deferred addresses:
22:43:14 30035 search_tidyup called
22:43:14 30035 >>>>>>>>>>>>>>>> Local deliveries >>>>>>>>>>>>>>>>
...
22:43:14 30035 LOG: MAIN
22:43:14 30035   == save Drafts <lolita@???> R=ldapsieve
T=address_directory defer (-21): appendfile: file or directory name
"Drafts" is not absolute
22:43:14 30035 >>>>>>>>>>>>>>>> deliveries are done >>>>>>>>>>>>>>>>
#######################################

Does anyone knows what's going wrong?