You may have noticed your emails looking a little cramped in Hotmail and Outlook.com recently. The culprit? Discontinuation of support for the margin property in these email clients. Rather than honoring your carefully spaced paragraphs and images, Hotmail and Outlook.com are now completely stripping margin from paragraph tags, leaving default values (0 for the top, right and left; 1.35em for the bottom, to be exact) in their place.

Yeah, as many developers will tell you, designing/coding for email is an incredibly hit-or-miss proposition...this is simply one more thing that may work in some email clients. The only consistent behavior in HTML/CSS emails is that nothing is consistent. :-)

I'm coding an email for a project and man! it's such a pain. Every other client has it's own implementation and supported rules. Some don't allow even simple properties like background-image while some support most advanced rules like media queries

That's something that has been bugging me too. I mean, it's fine if not everything is supported, but if everyone could agree on what is or should be supported then that would make a huge difference. But until then, it's going to be a struggle.

I've worked with people at companies where this was their only responsibility. Setting up emails for clients, making sure they pass a battery of tests and look great in all browsers and clients. It's an incredible PITA and it's not a set it and forget it thing. Clients can change month to month; spam filters change, etc...

There is a lot of variation in styling support among different mail clients