[Exim] rcpt_include_affixes not working for me

Hello all,

firstly, it was a toss up to post this either in exim or cyrus. I
finally decided exim for reasons you'll see in a minute. I am using
smtp/lmtp to deliver to cyrus.

I have in my router the following:

local_user_cyrus:
driver = accept
check_local_user
local_part_suffix = +*
local_part_suffix_optional
transport = local_delivery_cyrus

my transport:

local_delivery_cyrus:
driver = smtp
protocol = lmtp
rcpt_include_affixes
hosts = localhost
allow_localhost

All mail, regardless of having a suffix or not, is delivered to the
Inbox. I've tested cyrus by telnetting into it and and issuing manual
mail commands, and I can deliver into specifically targetted folders
this way, its only failing with 'real' mail. I am using the alternative
namespace feature in cyrus, but this shouldn't effect things, as my
manual message test works with it.

Can anyone help me with this ? I have the exim 4.30, cyrus 2.1.6

thanks