I know that Gmail might put some security measures in place to prevent this, but I really need to put Gmail inside an element.
The two following methods don't work:
<object type='text/html' data='http://mail.google.com/'></object>
<iframe src='http://mail.google.com/' frameborder=0 style='width:322px; height:480px;'></iframe>
Are there any other ways?
You cannot. GMail, like most of Google's other web services, sets the HTTP header:
X-Frame-Options: SAMEORIGIN
which disallows their site from being framed by any site other than GMail itself.
You would be better off using Google API. http://code.google.com/appengine/docs/python/mail/
Although not a solution to your question I believe this is an appropriate alternative.