I came across a handy add-on for Gmail (via lifehacker) called Right Inbox. It allows you to schedule e-mails to be sent at a specific time, which is cool in itself, but the more interesting feature is the ability to track e-mails. The majority of our query letters will go unanswered, but now you can determine if someone is actually reading them. I sent out a few and it worked like a charm. While the service is $4.95 a month for unlimited e-mails, there's also a free version limited to 10 e-mails monthly.