The primary reason we don't provide this at the moment is because of how imperfect Email Analytics is.
The easiest example is Gmail. Due to their image caching we can only detect that the email was opened by Gmail. We can't tell if that is Gmail in Firefox or the Gmail App for iOS. So there is no 1 to 1 connection to make.
There are several other, more subtle, distinctions as well. For example, Outlook for macOS uses the same user agent as Apple Mail. We default to saying Apple Mail for those opens but again it's an imperfect match.
This is a problem we've considered and we're considering potential solutions but nothing is imminent just yet.
We do use Gmail accounts on all our Gmail tests except for one Gmail Android IMAP.
I'm open an issue on our side to investigate but @Charlotte - if you could also email us at email@example.com that would be helpful to troubleshoot. It sounds like we should be matching those local tests.
I can say with some amount of confidence that the Gmail App on Android does strip the style tag and adds the head section below.
I saw someone allude to this once on twitter - I can't recall who it was so credit to that person if I can find them.
Also, I don't think they'd ever do this but here is what I'd like to see:
First thing to consider is why does MS use Word as a rendering engine? The primary reason I can see is to create a rich experience for their users. You can open Outlook, hit New Message, drag a Power Point presentation and an Excel doc in and hit send. When your coworker opens this message in their Outlook they can dive right into these docs in the message. It's a compelling use case and people are doing this at their jobs all day long.
Similar to how you could tell IE which versions you designed against with Compatibility Mode, we should be able to include a meta tag for render mode.
<meta http-equiv="X-Render-Mode" content="html" />
If this tag is present I know I am sending an HTML email. I am asking Outlook to use a browser control to render this message. I am consciously opting out of the MS Office ecosystem. Sure my messages will lose some functionality - I can't embed an Excel doc in them. I think providing a list of tags / css to support is silly. I want you to support all of them.
The technical challenge in this approach is how to handle when the user hits fwd or reply. Do you convert the message to a Word doc at that point? But surely they could tackle that challenge as opposed to the challenge of getting a Word control to support all the various HTML and CSS that people want to see.
It's in progress. We're overhauling our Android code to be able to update more easily going forward which is what's holding it up a bit. Keep an eye on our blog / twitter where we'll announce when we've updated.
I wrote a small python script to basically do just this. It will build your email from text and html and insert it into any webmail platform.
It's easy cause many designers are on a mac and have python already installed.
We follow the Android market share pretty closely. Unfortunately the uptick for 4.4 hasn't really happened just yet. When it does we'll definitely add support for it.