I just signed up with EOA and ran a test on an email. It appears as though the <style> tags are being stripped in the Gmail previews (both iOS/Android apps and web), as all of the email that had inline styles rendered fine, but tags that are relying on the <style> tags are being rendered without those styles.
Gmail stopped stripping <style> tags quite some time ago, and indeed when I test the email by actually sending it to a Gmail account and view it for real, the styles are working—ergo the preview is incorrect. Is there some reason why the previews haven’t been updated to reflect this?
Attached are screenshots of the EOA Gmail web preview + the email in actually rendered in Gmail web. The same results happen with iOS/Android apps (broken in EOA preview, correct in actual apps).
I think I found what’s going on. I guess maybe the preview is using GANGA? Can anyone confirm? See here for more info: https://www.emailonacid.com/blog/article/email-development/what-you-need-to-know-about-the-new-gmail-ios-update