[Exim] non-working user dns retrying too often, too quickly?

I am using exim 4.10 + exiscan 4.10-16

I have a message for a user with a non-working DNS and I am getting this
message every 10 seconds in my main and reject logs.

2002-10-15 14:45:11 H=localhost (post.tobit.co.uk) [127.0.0.1]
F=<dxspider-support-admin@???> temporarily rejected RCPT
<radioman@???>: host lookup did not complete

2002-10-15 14:45:21 H=localhost (post.tobit.co.uk) [127.0.0.1]
F=<dxspider-support-admin@???> temporarily rejected RCPT
<radioman@???>: host lookup did not complete