http://www.livejournal.com/support/faqbrowse.bml?faqid=19
The Email Management page displays all your previous email addresses, sorted by age, so your original email address is first on the list.
For your security, you can remove some of these previous email addresses in order to prevent them from receiving password reset emails. In order to do this, you must first change your email address to one that is earlier on the list, to help verify your identity. Once you do this, you can delete any later email addresses listed. Because of this, you cannot delete your first email address; this address cannot be removed from your list.
Proposed change
The Email Management page displays all your previous email addresses, sorted by age, so your original email address is first on the list. You may remove previous email addresses from this page, to prevent them from receiving password reset emails.
For your security, your previously validated email address cannot be removed from your account for a period of 6 months after your new email address has been added.
http://www.livejournal.com/support/faqbrowse.bml?faqid=117
Mentions email removal, will also need to be updated.