Why is Gmail blocking CSS in emails?

Question

I used CSS in my email and sent it out.

When I received the email in Gmail, all the CSS was disabled; however, when I retrieved the email in thunderbird or outlook,

Answer 1

If you're using Ruby on Rails and ActionMailer you can use the gem ActionMailer Inline CSS. All you have to do is install the gem and it will automatically inline all the CSS in your mail templates. It literally could not be easier.

ActionMailer Inline CSS on GitHub