This is very strange...
When I set a domain such as http://www.123abc.com as the Primary Domain mapping, it results in a redirect loop. To clarify, when I enter http://www.123abc.com in the browser, it redirects back to the default subdomain for the site (subsite.mainsite.com), and shows the "redirect loop" error message.
If I set any other domain name as the Primary domain that does not have numbers at the start of the domain, such as http://www.abc.com, domain mapping works perfectly.
I have 50+ other domain mappings working perfectly fine. This is the first one that includes a number, and it's not working.
Is it a bug in the plugin? What's going on? PLEASE HELP!