By the way, play button is a default thingie. Previously GIFs were not supported at all in most of the desktop clients, so at least we have it plaid once now. :D
I had the same problem yesterday. Problem was, that original GIF file was 1280x600px, while e-mail template was 640px, which resulted GIF out of scale 640x600px.
Fix: eksport your GIF in scale 1:1. e.g. 640x300px. This worked for me.
Let me know if this works for you too.
I just found this article: https://www.zdnet.com/article/microsoft-to-drop-outlook-on-the-web-mobile-apps-for-ios-android-by-mid-may/
It kind of makes sense why nothing works when I try to fix things only for Outlook app. Surprisingly mobile queries are working almost perfectly on Android, but it's a disaster on iOS - tons of problems with widths and god knows what.
Another headache - in most of my templates, I have to use floats (my company has some sort of analogical framework as Mailchimp and we have some predefined CSS). My guess is that the damn float blows up a little bit the td and the content inside of it (img and text) - and this happens only in Outlook app.
It really makes me mad. Every single morning I am checking for updates regarding all of this mess.
I'm having the same issue and can't stack content on top of each other in Outlook iOS! I'll be watching your post and if I find any functional solution, I'll definitely share.
Thanks for your reply.
EmailOnAcid has Gmail support for IOS, but they don't have the Gmail update which enables media quries. So you can get an advantage here, if you find the solution! ;)