I assume you are inserting the photos then dragging the 'ears' in to size. That is no good, the underlying file size has not changed. You need to use a program like the free Irfanview to resize your pics. Or you can set your camera to lower settings to take your photos. Don't set the camera lower if you wish to print any photos or the quality will be degraded a bit.

if you are using xp there is a very handy little windows power toy that puts a resize photo option in your right click context menu so that any picture you have on your pc you can just right click on it and select one of the smaller sizes offered or choose a custom size then use the smaller version when you attach it to your emails.
Go to this link scroll down to the image resizer option and download it to your pc
Image Resizer

for those with Vista there is no such powertoy but this image resizer does the same job.
Prish Image Resizer: PowerToy for Windows XP/Vista

Also sometimes you can simply right click and the send to, email and it will let you select a size have you tried that?

Irfanview is an excellent free program for sizing and manipulating photos. I always downsize before emailing. If the recipient needs a larger photo, I'll print and mail it. www.irfanview.com