MailTuner is a new utility that can fix the slowdown that users may see if they have a large number of contacts in the Mac OS X Address Book. This can slow down the built-in Mail program and cause the message "Adding contact to address book" to appear most of the time. MailTuner compresses the address book and forces it to update the address index.
What's new in MailTuner
Fixed a bug to allow the software to work in Panther (10.3)