I have a single domain with a dozen subdomains for different sites. Each has a separate virtual host in apache.
I configured sendmail to masquerad as the top-level domain so that emails are always from the top-level domain instead of the subdomain.
Unfortunately, DKIM header d= and i= fields show the subdomain. Since the DNS Record is stored at the top-level domain, the DKIM Check fails.
How do I tell DKIM to use the top-level domain?
p.s. I've tried every angle on this and I'm stumped. I can't figure out how Sendmail tells DKIM which subdomain to use. And I can't figure out how PHP tells Sendmail which subdomain is being used. I tried setting $_SERVER['SERVER_NAME'] to override it just before sending the mail, but it has no effect. I can't figure out a single work-around.