DIV problem when emailing html

I have created an html page in Dreamweaver 5 which is fine when previewed with IE or Chrome and when published.
I then email this HTML with the full URL using a mail marketing package to my customers. Everything is fine on the email except my left nav div. It looses some of the CSS but not all of them - for example, I still have the background and font colours but not the padding so my left nav is all squashed together!
This is the only div in this HTML page and it is placed in a table.
Please help.
PS: I am a beginner (ish)