Just an FYI for anyone that may run across this same issue:

Gmail does not evaluate !important as case-insensative. If for some reason you use style="FONT-SIZE:16PX !IMPORTANT", the uppercase use of !important will break Gmail's ability to evaluate this css. I believe that the css spec indicates that all css should be case-insensative.

Builder Example:
https://litmus.com/builder/e7d5e7e

First a tag uses lowercase important, second uses uppercase.

Sam