The Gmail App is notorious - this explains some of the issues better than I can https://www.emailonacid.com/blog/article/email-development/12_things_you_must_know_when_developing_for_gmail_and_gmail_mobile_apps-2/
Apologies if I'm telling you something you already know!
Thanks - that gives me a much clearer insight into the why as well as the how. I'd always followed the rules of jpg for photos and GIF (hard G) for graphics but haven't been sure where the PNG fits in. I'm often required to use text-on-gradient-on-photo and getting the best quality has often been a nightmare!
I got myself a lot of extra creative control of email within our organisation.
It is a very traditional non-ecommerce business and email marketing is regarded mainly as sticking a header image over a page of text - we send to over 60% Outlook users so often this is still the safest way!
I had no access to any html editors so most of my learning and development was done in notepad and then viewed in an ie window, you can well imagine this took forever to get anything done.
When I discovered Litmus builder it gave me the space to get more creative and implement techniques and designs that would be much more appealing to the eye, even in outlook! Being able to show these to my senior managers opened a few eyes and demonstrated there were more creative options to building emails than text or sliced up images.
Since having the extra freedom I've been able to develop solid templates for the day to day work allowing extra development time for larger projects seeing a leap in open to click go from 10% to 30%+ in many cases.
I've got a good self improvement regime that involves stalking the email community on social media and studying the code of any emails I like. I find being advanced is overrated if you aren't adding any value and distracting from the message, but occasionally you will find an absolute gem that is worth deconstructing and "borrowing" for one of my own designs.
Just seen this post - I had plenty of issues with the buttons as well that we being absolutely butchered when they hit Outlook.
After several weeks banging my head I worked out it was to do with the unsupported version of Chrome I was using when creating the email - it worked fine again when we finally got a browser upgrade and when using IE.
I hope you managed to sort it our in the end!
I've started a bit of a battle with the ESP on this one who made the change and won't accept my Litmus images as proof there's an issue . I'll have to go back to my own buttons until they revert to the non-VML style.
If it ain't broke, don't fix it!