I changed the domain name for a subsite on my WPMU, from old-domain.com to new-domain.com.
I set the new-domain.com to be primary and kept the old-domain.com as secondary. Now, going to an old page URL automatically redirects and shows the corresponding new URL page. Yet Google instructs to do 301 redirects for pages pointing to the new address but using the Domain Mapping plugin...
Does the plugin do a 301 in the background or does this work in some other way that will not require doing 301s?
Am I losing any Google juice if I don't also implement 301s?