DomainKeys and DKIM signing support

Julian Field MailScanner at
Thu Jun 7 17:46:54 IST 2007

Kevin Hansard wrote:
> I would like to sign my outgoing emails with a DomainKeys or DKIM
> signature. I have looked at using dkim-filter with sendmail to perform
> this however the solution doesn't really work with MailScanner because
> milters can only operate on incoming SMTP messages, so if MailScanner
> makes any changes to the message the signature will be invalidated. In
> our system we add a disclaimer using MailScanner to messages so the body
> signature would always be invalid.
> It seems sensible for MailScanner to perform this function immediately
> before submitting the message for delivery. I don't think it would be
> that hard to implement given the Mail::DKIM module would do most of the
> work. However I am reluctant to start hacking the MailScanner code.
> Is DKIM support on the MailScanner roadmap?
Not yet, no; but it could be.
Have you got a nice simple short and sweet document describing DKIM, how 
it works, what it protects against and why it will stop all spam :-)

> Has anyone else ran into this issue?
Assuming it's based on some checksum/hash function, what text of the 
message does it use as its input?
Can you make it just operate on the body and not the headers at all?

Am I just trying to add DKIM to a message, or do you need me to check it 
as well?
> Alternative solutions would including placing the messages to be signed
> in a different queue and have my own app sign them and put them back
> into the main outgoing queue or using another sendmail gateway running
> dkim-filter to process the messages coming out of MailScanner.
> Thoughts appreciated.
> Thanks
> --
> Kevin Hansard


Julian Field MEng CITP
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