Another of my bugbears with email design is seeing images amongst text, aligned right for example and not having any thoughts about padding around the image. Whether or not the designer intended there to be padding and my email client has been blissfully unaware, I don't know. One way or the other, slapping an image in amidst text can be a real pain in the rear end when you don't have the kind of control over an image as you would on a traditional website.
There are a few ways around this, the easiest is to crop the image with the padding built in, usually to the left and bottom (if aligned right) or to the right and bottom (if aligned left), just insert the image and align as required. Job done. It's guaranteed to work in every email client that can display images.
Failing that, if you want to keep the image cropped to the very edges, try placing the image in a container of sorts (either a table or a div), apply your padding with inline styles and then align
that to the left or right.
Off the top of my head, I know that simply applying a margin inline on an image won't work in the red-headed bastard step child that is Outlook 2007 (and I've seen people try to add padding, how does that work exactly?!) so it's probably worth ignoring, even if every other email client out there does support it.