I just happened to stumble across this old post while I was Googling something related. Just in case anyone finds themselves asking the same question, the basic answer is no, there isn't anything that you can do on your iPad to reduce or stop spam emails.
What you can do is configure the spam filter(s) on your email server or with your ISP. Mail servers employ applications that filter spam, viruses, etc. (most often SpamAssassin) and they can be adjusted to intercept emails suspected of being spam. They usually have a feature that allows you to create black and white lists that will block or allow specific email addresses and/or IP addresses as well.
Hope that helps!
