A couple years ago we ran a 1 day sale in the beginning of December. We were sending to a customer list of over 22 million. We did not know that yahoo mail had started throttling email to something like ~200k per hour for the holiday season. The next day we started to get emails from customers that they had just received the email but the sale was over. Major fail! After this experience we started to plan emails around this new throttling and we also started separating our yahoo sends and throttling the deployments to stay within the max per hour.
I was hired at my current company as an email developer. After working there a couple weeks I got familiar with their entire process and quickly realized they needed an upgrade. I wrote up a proposal and highlighted all of the changes that I saw possible if they switched to Responsys as their ESP. I saw noticed many scenarios for the email team to make use of the Built in Functions that Responsys offered and ultimately make the entire team much more efficient. The proposal was taken right up to the VP of Operations and then the COO. Everyone was onboard with the change and I took charge of the entire implementation from pricing out to warm up, ramp up, and even laying out the new process for the email team to follow.
I had! I couldn't find anything that specifically said you couldn't use attribute selectors. That's how I ended up testing and testing until I was able to get my emails to work. Even gmail support does say you can't use them. https://developers.google.com/gmail/design/css
Make sure to double check your CSS. None of my email displayed responsive until I did this https://litmus.com/community/discussions/5938-coding-responsive-email-in-gmail-app