dkim signing by an email service provider

From: Daniel Black <daniel.subs_at_internode.on.net>
Date: Fri, 30 Nov 2012 10:31:46 +1100

Wondering how other people go about setting up DKIM signing as a service
provider. So the service provider is providing an outbound email service
for a number of email clients.

My initial thoughts are to provide a DKIM signature on the domain of the
service provider, and a DKIM signature that is configurable by the
client on the client's domain.

Anyone have any thoughts how two valid signatures would be handled in
the logic on email receivers?

I looked at a Google Apps hosted domain and it adds a
X-Google-DKIM-Signature header field which is the DKIM signature. How
odd. I've also seen an option to add DKIM signatures on the client
domain in their management interfaces. I haven't noticed if they omit
their signature if the client domain signature is there. Maybe that is a
better option?

Of course this is all possible with opendkim (multiple signatures and
keytables and signing tables).

Daniel
Received on Thu Nov 29 2012 - 23:31:58 PST