Help please - My GIFs in Campaign builder are not appearing in emails

Hello Community!
I was hoping you could help me - I’ve spend some time getting a load of GIFs created for my Infusionsoft campaigns. They play fine in ‘Preview’, but when sent to certain people, even once they have clicked ‘show content/ images’, the following ‘broken image icon’ appears where the GIF should appear:


The GIF comes through fine when I send it to myself, but when I’ve tested it with all of my colleagues, this ‘broken image icon’ appears every time.
I have tested sending the GIF alone from Outlook to Outlook (to my colleagues computer) and it works fine, so Infusionsoft seem to be stripping out some of the code.

We use Outlook 365 (web version), but the problem may occur with other web browsers, which is what I’m worried about.

ANY advice would be greatly appreciated.
If I have to recreate my GIFs, what should I do differently?

Many thanks in advance!