CSS Classes in the HTML Tag

Your software
My Mautic version is: 2.15.3
My PHP version is: 7.0.33-15+ubuntu16.04.1+deb.sury.org+1

Your problem
My problem is:
We are noticing a bunch of classes are getting added to the html tag when we create an email using a theme template. Any ideas for a fix?

Here are the classes added:
class=" js flexbox flexboxlegacy canvas canvastext webgl no-touch geolocation postmessage websqldatabase indexeddb hashchange history draganddrop websockets rgba hsla multiplebgs backgroundsize borderimage borderradius boxshadow textshadow opacity cssanimations csscolumns cssgradients cssreflections csstransforms csstransforms3d csstransitions fontface generatedcontent video audio localstorage sessionstorage webworkers applicationcache svg inlinesvg smil svgclippaths js csstransforms csstransforms3d csstransitions responsejs "

Hi, which theme are you exactly using?
Those css classes are actually used in the email - so they are needed.
You can also create your own HTML email and copy it in as code mode.
Good luck.

We actually created our own theme. We noticed the classes because they were triggering an error in glockapps, which we use to check our emails before sending. Do the classes for the other themes want to be in the html tag, and if we aren’t using them, would it be possible to remove them in our theme?
Thanks in advance for the help!