I faced the same problem once while generating mobi from epub by dragging epub on kindle previewer. I resolved this problem by generating the mobi using Kindlegen.exe instead of using kindle previewer to generate mobi. See if this helps you.

Hi James,
In case you have not figured it out yet…here the trick
You can get the ePub from your mobi easily by importing it to the Kindle Comic Creator tool. As soon as you import, it gives you ePub at the same location of you file. You can make the desired changes in the CSS and generate mobi from it.

I tried it and found it little more tricky. You need to add
a{text-decoration:none !important;}
to your CSS to make it work in kindle(don’t forget to add !important).

Hope this helps.