Hi Steve,
You should be able to find the blocked user by logging in as the System Admin and going to Manage section > IDS Blocks. Click on the Webmail tab, then use the [...] button to Unblock the IP.
Alternatively, if you restart the SmarterMail service, it will undo the brute force lock as well.
Andrea Free
SmarterTools Inc.
877-357-6278
www.smartertools.com