Hey there,
After reviewing your project description its clear that you have problem with OpenDKIM
I'm very experienced with System Administration, Network Administration, SMTP Server Configuration and Troubleshooting, SMTP Authentication(SPF, Dkim, Dmarc, rDNS), SMTP IP/Domain Reputation.
I'll be happy to do this project for you.
Thanks in advance for giving the opportunity to working with you.
Have a good day.
Best Regards,
Serazum Munir.