Today I released a new major version of premailer where the only difference is that one of the default options have changed from True to False.
The git commit for this change might look big but the only difference is that now, by default, the HTML class attribute is kept in the output HTML.
When premailer started, the land of HTML emails was very different. Basically, you used to not use CSS media queries, so, no reason to keep the class attribute. Now, these days, all pretty HTML emails need media queries and for that to work you need to have the class attribute kept in the HTML.
So fear not the major version upgrade! If you used to use premailer like this:
frompremailerimportPremailertransformer=Premailer(html)output_html=transformer.transform()
You now need to change it to:
frompremailerimportPremailertransformer=Premailer(html,remove_classes=True)output_html=transformer.transform()
As always, you can play with it on premailer.io.