This mod was originally written by someone else (cannot recall whom) but I reinvented the wheel by modifying my IP search routine. The mod enables administrators to search EMail addresses for specific addresses or for substrings (any portion of the address, i.e., all hotmail or anyone with the word sex). The results can be further refined by limiting output to new members, to today's visitors, etc.
You can get a copy here:
http://www.snitzbitz.com/mods/details.asp?Version=All&mid=264<