Is there a way to empty the outgoing e-mail queue

I did a bad thing. Wrote an event to send me an e-mail if a certain device goes offline. It did and generated THOUSANDS of e-mails, which have been queued *somewhere*. G-mail stopped accepting them, so but plucky little HS3 keeps trying to send just the same, filling the log with errors and retries.

Is there a place that I can wipe out the queue of e-mails waiting to be sent?