I try to setup DKIM signing for outgoing mail on our C300D appliance with 7.1.2-020 AsyncOS but I could not get rid of that "cannot sign - no identifiable sending address" issue.
I've a public and private IP interface. I inject mail to the Private listener with RELAYED activated for my sender group 192.168.0.x. I've defined a outgoing filter which detects mails injected from the private listener to deliver them through the public interface (alt-src-host). On the RELAYED Mail flow policy for the public interface, I've activated the DKIM signing.
I've also defined two profiles for DK and DKIM with the same key. DNS records are ok, test is ok. For those profiles, I've defined a sender user [email protected].
So when I telnet to the private interface and forge a test mail to check with myiptest website :
MAIL FROM:<[email protected]>
RCPT TO:<[email protected]>