[exim] Problem with DKIM signature verification

Hi,

I have found in exim mainlog many messages like the following:

1ZDea7-00063r-Px DKIM: d=gmail.com s=20120113 c=relaxed/relaxed a=rsa-sha256 [verification failed - signature did not verify (headers probably modified in transit)]
or
DKIM: d=gmail.com s=20120113 c=relaxed/relaxed a=rsa-sha256 [verification failed - signature did not verify (headers probably modified in transit)]
or
DKIM: d=blueloop.net s=2896446 c=relaxed/relaxed a=rsa-sha256 [verification failed - body hash mismatch (body probably modified in transit)]

They are mainly related to lists mails. Most of the time it complains about headers, and sometimes about the body.

Is it a configuration problem at my side ?

I don’t have any idea at where to look.

Thanks in advance

Regards

nb