Mass (spam) emails seeking short term internship, solutions
What I do is to provide on my web page a very explicit set of directions for how to contact me about possibly doing any kind of work with my group. I have separate sections for undergrads, grads, and postdocs. For undergrads, I explain a bit about what we do in my group, describe what undergrad research in the group is like, ask them to answer a few questions about what draws them to our work in particular, what they hope to gain by working with us, about their skills and background, and about their general interest and experience reading primary literature. I also ask for a transcript. You could ask anything, though. 

With something like this in place, you can either ignore with good conscience any emails that fail to address these questions, or you can send a brief form-letter response asking that the applicant address these questions in order to be considered for a position.