There is something weird with testing out my DKIM signature. As suggested I used http://dkimvalidator.com but it shows me that my signature is not valid:
0.1 DKIM_INVALID DKIM or DK signature exists, but is not valid
When I send an Email to myself and check all the parameter within roundcube there are no such issues and my DKIM signature is shown as valid. Besides that I tested it at http://www.appmaildev.com/en/dkim and there is no such issue, too - result: DKIM passed.
Does anybody has an idea of what’s wrong as only http://dkimvalidator.com is telling me that my DKIM signature is invalid?