Im not sure about fixing it with a DNS entry. Both the http://www.example.com and example.com already resolves to the same IP address.
I have my main setup running at...
its a subdomain, not a tld, so this might a problem, i dont know.
Then I have a domain mapping like this...
http://wp.mymainsite.com/site1 --> http://www.example.com
which works fine.
However, when I type the domain without www leading, like...
http://example.com I would expect two things, which neither happens.
1- it redirect to the http://www.example.com or
2- it serves the site as it has been typed like http://example.com
I do not expect it to redirect the request to the main site, which happens unexpectedly...
http://example.com --> http://wp.mainsite.com
Now, I can add another domain mapping entry for the non-www version of my additional website
http://wp.mymainsite.com/site1 --> http://example.com
This will prevent non-www entries to my additional site to redirect to the main site.
Now the new problem is I have two different versions of my website running with and without the www leading. Which it should not.
A rewrite rule which redirects all non-www requests to the http://www.example.com in .htaccess will solve the problem. Which, I have not been able to write that entry yet.
This MAY or MAY NOT be a problem or bug with the plug-in. I really do not know. This might be the way it works by design. If it is the way it works, maybe this issue should be documented.
@BackuPs, please tell me about your setup. How is your setup works out of the box?