The handling of email attachments is a pretty important function for a mobile operating system. Windows Mobile historically handles them much like Windows on the desktop: you can tap to download an attachment, and either have the option to Open or Save it somewhere. In Windows Phone 7, as we can see by the below video (jump to 2:36), attachments are handled much like Android but a bit like the iPhone: you're given an index of all of the attachments on a given email, placed at the top.
Before each item is downloaded they share a common icon, in this case, a paperclip. Once an item is downloaded, the paperclip changes into the application icon, and from there you can tap to open it. What we don't get to see is if, like Android, a long press will allow you to save the attachment in a file of your choice. Our guess is "no" to this question, since Windows Phone 7 doesn't have a file manager so there would be no way to access saved attachments.