Hi
Either export your project with different resolution settings as Borate suggests, so choosing a smaller format or you could use a third party Video converter such as the free Any Video Converter Output format such as Flash swf or flv are generally smaller that .avi. This free software can convert a large number of formats and resolutions.
http://www.any-video-converter.com/products/for_video_free/
NCH also have a video converter called Prism for doing the same thing.
You would have to reduce your video quite a bit for mailing as there is often a file size limit for attachments.
e.g. With AVC ....A 7 min MPEG4 1280 x 720 avi file was 167 Mb. This converted to a 320 x 240 swf clip of 27 Mb. Still a bit big.
With VP........The same avi exported to a 320 x 240 swf file of 18Mb
Nat