Mail Handlers perform case sensitive lookup of usernames

1. Create a user with the username test@example.com
2. Set their email address to something else e.g. noreply@example.com
3. Send a message to JIRA from Test@example.com - note that the mail client has uppercased the address

Now when JIRA tries to find the user it will look first for the email address and if its not found it will try and use the email address as the username. However the comparison will be done in a case sensitive manner, so Test@example.com won't be found and JIRA will try and create a new user and force the email address to lowercase when doing so. This results in an error similar to the following:

2009-06-30 14:50:04,191 JiraQuartzScheduler_Worker-2 ERROR [service.util.handler.AbstractMessageHandler] Error occurred while automatically creating a new u
ser from email:
com.opensymphony.user.DuplicateEntityException: The user Test@example.com already exists.
at com.atlassian.core.user.UserUtils.createUser(UserUtils.java:261)
at com.atlassian.core.user.UserUtils.createUser(UserUtils.java:238)