[exim] Keep local_part_suffix in redirect router

Hello,

we'd like to allow subaddresses like user+sub@domain to deliver to users’s folder sub (if existent) via lmtp. Target system is cyrus-imapd.
We have these routers:

global_aliases:
driver = redirect
allow_defer
allow_fail
data = ${lookup{$local_part@$domain}dbm{DBM/aliases}}
local_part_suffix = "+*"
local_part_suffix_optional
retry_use_local_part
no_rewrite

local_user:
driver = accept
domains = mailbox.hrz.tu-chemnitz.de : mail.tu-chemnitz.de
no_check_local_user
transport = lmtp
…

and this transport:

lmtp:
driver = smtp
protocol = lmtp
hosts = host1
rcpt_include_affixes = true
delivery_date_add

Running
/usr/sbin/exim -v -d-all+route -bvfri+test@???
shows:

routingfri+test@???
------- global_aliases router -------
local_part=fri+test domain=hrz.tu-chemnitz.de
stripped suffix +test
calling global_aliases router
rda_interpret (string): '${lookup{$local_part@$domain}dbm{/path/aliases}}'
expanded: 'fri@???'
file is not a filter file
parse_forward_list:fri@???
extract item:fri@???
global_aliases router generatedfri@???
errors_to=NULL transport=NULL
uid=unset gid=unset home=NULL
routed by global_aliases router
envelope to:fri+test@???
transport: <none>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

routingfri@???
--------> global_aliases router <--------
local_part=fri domain=mailbox.hrz.tu-chemnitz.de
calling global_aliases router
rda_interpret (string): '${lookup{$local_part@$domain}dbm{/path/aliases}}'
expanded: ''
file is not a filter file
parse_forward_list:
global_aliases router declined forfri@???
------- local_user router -------
local_part=fri domain=mailbox.hrz.tu-chemnitz.de
checking domains
calling local_user router
local_user router called forfri@???
   domain = mailbox.hrz.tu-chemnitz.de
set transport lmtp
queued for lmtp transport: local_part = fri
domain = mailbox.hrz.tu-chemnitz.de
   errors_to=NULL
   domain_data=mailbox.hrz.tu-chemnitz.de local_part_data=NULL
routed by local_user router
   envelope to:fri@???
   transport: lmtp
fri@???
     <--fri+test@???
   router = local_user, transport = lmtp

→ the suffix +test is gone here.

Does anybody has a hint how to keep the subaddress to the lmtp transport?

Thanks,
Frank

--
Frank Richter, Chemnitz University of Technology, Germany