[Exim] SMTP error from remote mailer after STARTTL

Hi

having searched through archive I found the same problem
I have:

Problem:
when sending mails to some addresses, I get this error:
SMTP error from remote mailer after STARTTLS: host
mvs.mediaways.net
[62.53.235.28]: 454 TLS not available: missing RSA
private key (#4.3.0):
retry timeout exceeded?

Answer:
It means the remote end has been told to advertise
STARTTLS, but is in fact not configured with the proper
TLS certificates and keys. I've also seen Exchange
servers which has been misconfigured like that. It
shouldn't be a problem though, as exim should just ignore
the error, and deliver without using TLS.

BUT: in our config, exim does not ignore the error.
instead it sends a non-delivery. We use exim 3.2. I know
we should have updated long time ago. This is planned,
but before, we need to solve the above problem.

any idea? thanks
bettina