When you paste into an email, there is usually two options. Paste as plain text or Paste. If you just use Paste it should keep your formatting. Sometimes, though, the auto corrects in the original document look like alien script once you send it. So you may want to send a copy to yourself first to see how it formats on the other end.
Also, you can copy your text first in a Word document, then turn off the auto formatting, replacing apostrophes, quotation marks, double dashes w/ standard and not smart formats. Also, make sure you select No Spacing, and double space from the paragraph format tab. All this I have discovered so as not to have to go in and manually double space the email sample.