Holy fucking shit are email clients bullshit.
I don't know what happened there but if you thought the chrome-firefox-ie-egde gaps back in the days were sick - let me tell you.. email clients are made by the devil himself. All of them. All of them? Yup. Because he made some of them being owned by apple, working beatuiful and no weird stuff.
But on the same end he made some of them owned by microsoft and their office Studios. They use the word engine to render html emails. Read this again. Read it without starting to cry in agony.
But thats not enough. Let's make some of them use an ie-engine and the mac os variants going to use some webkit based renderer. This way there will be no valid ruleset to make it look good on all of them, isn't this great??
Now this might be hell already. But lets pour more salt into these wide opened wounds.
Let there be Germany and United Internet, owning trash like Web.de and GMX, whose android clients going to work completely different across Android and app-versions!
Once you've mastered these, let me introduce you to gmail. Lets take only the body node of your email and do some fuck up with it, so you have to display a non-responsive variant on mobile.
Now you might be thinking "but there are web-based clients, they'll do good ain't they?" Long story short: fuck you.
Not enough.
Let's go back to ms.
Hey dude lets make it possible to scale up your whole system. So old people can read shit better. And now the funny part: let's make it so that the word rendering engine, rendering emails goes completely mayhem on your mail, so it looks like a completely different thing! (:

If you ever receive a newsletter in your inbox and that shit looks like it's planned to look like.. appreciate that shit. Sacrifice a virgin as thanksgiving for it.

TL;DR:
E-Mail needs to die. I'm doing this for over 2 years now and this shit needs to stop asap.