Thanks for reading and replying with such detail, Lisa. I have asked for years why GovDelivery doesn't provide this data, when free services (e.g., MailChimp) as well as direct competitors to GovD do provide it. As you observe, it's industry standard data, so the omission is quite obvious.
What would I do with the data? For starters, if I saw we had more mobile viewers, I'd revise our GovD template designs, which are responsive, but don't scale intelligently--that is, with each type of content scaling appropriately. In this example, you can see that the header image was scaled down to fit my mobile screen, which is good. However, all the text was also scaled down at the same rate as the header image, which makes it nearly unreadable. The "Share" button just under the header image is almost invisible--and good luck tapping exactly on it on your first try.
On a desktop computer, of course, this all looks fine.
After we resized the text, I'd take another look at that banner and see if it's really the best we can do for small screens--if I knew that most of our folks were viewing messages on mobile.
So, as a start, if I had desktop vs. mobile data, I'd revise our templates accordingly. Then I'd look at open and click rates on the two platforms and see if we're getting more engagement on one and again revise our methods accordingly. For example, perhaps our text links aren't as noticeable on mobile and converting them all to buttons (using the handy automatic GovD H3 + link formatting, of course) would increase mobile engagement.
Those are what come readily to mind as possible easy wins, but it could be that we rethink other elements if we see high mobile engagement. It could also be that if we see high mobile email engagement, we ask our employees if they prefer email or text messages, and make changes accordingly. Unfortunately, these are all hypothetical.
With data we could make decisions. In the dark, we can only guess if we're going in the right direction. If you have further questions, please let me know.