I created a table with borders -- but when i send a sample email to myself, the border lines get removed

hello -

I am not the most html savvy person and I mainly work with basic content. I have a table with boarders in my email and it looks fine when I preview the draft, but the border disappears when I send myself a sample. It looks fine on dreamweaver and in 'preview draft', but it doesn't look like that when it's sent.  Has anyone encountered this situation? How did you go about it?

thanks!