Inline CSS styles not displaying properly in email after being generated from PHP form handler

Keep in mind that this can be different depending on the client and clients change a lot. for example I had issues similar to what you are facing from the outlook from ios and on windows and other clients too. You have to test and build your html to work in multiple outdated IE based engines.

I suggest you test your code in one of the tools listed in this question: Testing HTML email rendering

I used https://email2go.io/home to fix my layouts.

Hope it helped.