Files that contain the .ctt file extension are used by the Microsoft Windows Live Messenger instant messaging software application. Windows Messenger is a free instant message application that is distributed by the Microsoft Corporation.
The CTT files that are used by the Windows Messenger IM application store a user's contact information in the XML file format. CTT files contain information such as the names and email addresses of a user's list of contacts. These files can be imported by another use to share contact lists and contact information. CTT files can also be helpful if a user loses his or her contact information, providing a backup resource of the user's contact files.
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