I know that this question is old since I've found many discussion when I searched. But none of the proposed solutions work in my case. My solution uses Umbraco 7.4.3.

I have tried so far:

1. Set useDomainPrefixes to true;

2. Add following to tinyMCE.config:

     <config key="convert_urls">false</config>
     <config key="relative_urls">false</config>
     <config key="remove_script_host">false</config>
   

3. Set the hostname on root node.

But nothing of these worked. Any one has any idea how I could make this work?