[Exim] hosts_avoid_esmtp

Hi,
I have exim 4.30 passing mail to exchange 5.5. It works ok except I get
messages in the exchange boxes event viewer about being unable to
complete the STARTTLS command issued by the exim box. I've tried using:

hostlist hosts_avoid_tls = the.exchange.box
hostlist hosts_avoid_esmtp = the.exchange.box

But the "problem" remains.

Any pointers would be appreciated.
Cheers

--
Pete