Using an existing DKIM signing solution to attach DKIM Core tokens

DKIM Core is just a subset of DKIM, so any smarthost or appliance that does DKIM signing can be used to attach DKIM Core tokens.

The details of how to configure this will vary depending on the details of the DKIM signer, but it should be configured as follows:

Header canonicalization:relaxed
Body canonicalization:simple
Signing algorithm:rsa-sha256
Signing domain:the DKIM Core token
User or Agent Identity:leave empty
Body length count:leave empty
Query method:leave empty
Selector:use a selector generated as described above
Signature timestamp:disable
Signature Expiration:disable
Copied header fields:none
Key granularity:disable, or set to “*” if that isn’t possible
Key type:rsa
Acceptable hash algorithms:leave empty
Notes:set to “core”
Service Type:disable
Flags:set to “s”