I don't think so. iPad apps can't interact with each other, so ad blocking would have to be built into the browser itself. Fortunately, such browsers exist, Mercury for example.
The best way to block spam email is at the server. If your ISP isn't already doing that, you can do as I do and route all your email addresses through a free gmail IMAP account, which offers both excellent spam filtering and an easy way to create your own custom filters as necessary. It's a little effort to set up, but then you can forget about it--it just works.
milliHelen: amount of beauty required to launch one ship.