This isn't actually a SWconnect question, but more a Spotwalla question. Perhaps Jason will chime in, but in general you don't need to download the trip, but instead you allow the trip to be shared (make it public, not private), and then you simply include a link to the trip web page in your email. The recipient would need to have access to the internet to see this however.
Another couple of options:
1. Trip setup allows you to specify whether or not the trip data can be downloaded. If I remember correct the trip data can be downloaded in several formats. None of the formats however are a "map". They do contain location information that can be brought into something like google maps, or google earth for visualization.
2. You could also view a trip on your computer, and screen capture the "map" as an image, and email that.
Since the trips essentially last forever on Spotwalla, I simply make it a public trip (not "private" in the trip setup), and then email a link to anyone that you might want to view it.