DKIM signatures from mailing lists

[dodmi]

I'm a member of a Google Groups mailing list.

The mails, which I receive have a valid DKIM signature from googlegroups.com. The from tag contains the original author's address. The sender tag contains <name of the list>@googlegroups.com
At the moment, there are two possibile DKIM results:
a) If there's no sign rule for the address of the author, I'll get a warning, because the author's address is from another domain.
b) If there is a sign rule for the address of the author, I'll get an error, because the signature is from the wrong domain.

I'm unhappy with this situation. But I'm not really sure, if also looking at the sender tag in general is a good idea. So I'd like to get some input before trying to change something.

[dodmi]

To answer myself: It‘s already possible to solve this: You can create a custom rule based on the listid tag and this rule will handle both cases, so that the DKIM result will be positive.