DKIM - RFC 4871 -

[Mail List]

> signatures in this message too - if you added verify to your sendmail they
> would be verified too.

Interestingly - when the mailling list sent my own signed message back it 
failed verification!

 the 2 parts that are signed - first is a suite of headers - one of which is 
sender - the mail list manager replaced the sender header removing the 
original one (with my email address) and replacing it with fedora-bounces. Of 
course this cannot be verified anymore.

This suggests that the Sender: field should not be signed - for mailing lists 
anyway - From and the remaining  fields could continue to be used.