Lifehacker has a link to a helpful article explaining the best way to ensure a response to your email, and, while it’s aimed at academics, we think the suggestions apply to customer complaints—or even when emailing this website. For example:
Write a clear and descriptive subject line. The reason for carefully crafting the subject line is two-fold. First, you want to make sure your message is not filtered out by a program as spam. Second, you want to make sure the recipient does not delete your note manually, assuming it is unwanted junk mail.
We would also add—before you send the email, think about what the most compelling thing about your complaint is, then clearly state it in as few words as possible. This will help CSRs get a clear idea of what your problem is, or, if you’re sending us an email—we might actually open it, thinking it’s not spam! —MEGHANN MARCO
A Primer on Electronic Communication [Inside Higher Ed via Lifehacker]