[Exim] ETRN again...

hi listeners,
i got a little problem here...

my exim accepts and stores emails for a customers domain
in a single pop-account.
the mailserver on customers side (running apple share ip)
connects to our mailserver, gets his mails via pop3 and
diconnects.

so far, so good, here's my problem:
the apple share ip server has its difficulties with sorting
the mails to the users mailboxes. 90% of the mails are forwarded
to the postmaster-account. i've tried to solve this with the
"envelope-to"-command, no use. in the apple knowledge base
was that article talking about etrn as an solution, as it is supported
by the asip server.

my question:
is it possible to forward the emails from that pop-mailbox to the
customers mailserver via etrn?

thx,

--
carpe noctem!
marcus