My native language is spanish and I'm fluent in english; I also have a very, very, very, very vague understanding of german, french, italian, and portuguese. Add the fact that most support emails are "the download link doesn't work", so if you can pick up just a few key words, you can usually understand what people whant.
What I do in these cases is offer an apology for not being able to respond in their native language, then my guess about what did they want, and how to solve it. Finally, another apology and "If I misunderstood you, please let me know what can I do for you".
So far, I always guessed right, and nobody ever complained by my lack of understanding of their language.