My GIF file does not work with Outlook.

Microsoft Office suite version 2007 does not support animated GIF images anymore.

There are no known workarounds for this at the moment, except for the following suggestion from Microsoft:

To play animated GIF (GIF: A graphics file format (.gif extension in Windows) used to display indexed-color graphics on the World Wide Web. It supports up to 256 colors and uses lossless compression, meaning that no image data is lost when the file is compressed.) files, you must open the files in the Preview/Properties window. To do this, select the animated GIF file, and then on the View menu, click Preview/Properties.