Email queue stops sending

We have a user that has been removed from the system, but who still has an outstanding subscription in the email queue that I believe is causing our mail queue to clog and stop sending. This may be resolved by issue JIRA-2487, but I need a workaround.

In the mail queue, there is always an item that says "Subscription: Everything... Jan 15, 2003" with no errors.

The stack trace is:

[10:53:43,622,Default] com.opensymphony.module.user.EntityNotFoundException: No user ~@!#@!# found
at com.opensymphony.module.user.UserManager.getEntity(UserManager.java:306)
at com.opensymphony.module.user.UserManager.getUser(UserManager.java:120)
at com.atlassian.jira.mail.SubscriptionMailQueueItem.send(SubscriptionMailQueueItem.java:70)
at com.atlassian.jira.mail.MailQueueImpl.sendBuffer(MailQueueImpl.java:52)
at com.atlassian.jira.web.action.admin.MailQueueAdmin.doExecute(MailQueueAdmin.java:24)

Where is the mail queue stored? Is it in a table in the db? I have perused the tables and can't seem to find anyplace I can remove this lingering subscription. My hope is that removing this entry from the queue will allow the queue to function properly.

Flushing the mail queue will flush any clogged notifications, but this one entry still remains.