Yes and no. If you go to File > Convert to a web page, Publisher will
convert your card and allow you to send the first page only. Publisher will
truncate the length of the page after the last design element on the page.
Perhaps start a new publication > Websites and email > Email > Letter . This
will give you a single page in a better width for emailing, and you can
change the design as you want.
Alternatively, convert your card to a PDF and send that. A free PDF tool:
www.primopdf.com
DavidF