I receive a lot of email signed with DKIM. Usually I am not interested in checking that the signature is valid, but every now and then I would like to. Is there any tool to which I can feed the email as it is, which checks it (possibly retrieving keys via DNS or whatever) and tells me if the signature is correct or not and maybe other useful details?
Besides the already mentioned Thunderbird DKIM Verifier add-on, I can also recommend the Python module dkimpy for this. Under Debian and Ubuntu, it is available in the python-dkim package.
With dkimpy you can easily verify the DKIM signature with the
dkimverify < email.eml command. To get more information why a signature is failing, use the
If you use Thunderbird, you can use the "DKIM Verifier" extension.
You can also use http://www.opendkim.org/ which comes as a debian package:
opendkim-testmsg < email.eml