I'm confused!
If you send a picture as an attachment to an e-mail, with Outlook Express, the file on the recipient's PC will be identical to the one on your PC (so there can be no loss of quality). The only problem is that, if you've used the highest resolution settings on a digital camera (which, for most purposes, is utterly pointless and best avoided), you'll be sending some very large files.
If your file sizes are too big to conveniently send as attachments, you need to do some experimenting with programs which allow file compression and/or resizing to get some results which look OK on your screen. Then save those compressed or re-sized images to a separate folder and send them as attachments.
If you're lucky enough to have Photoshop, the 'Save for web' function is handy for this. Otherwise, Irfanview has some useful features.
If the images are being printed out by the recipient, you need to remember that you can't compress files as much as if they're simply being viewed on a PC. For example, photographs on web pages often have file sizes around 30 to 50Kb. Trying to get a decent print from those images is very difficult because, for a decent print of the same size, there probably needs to be at least 500Kb of data.
Whichever software you use for file compression, work on the basis that the file size needs to end up as around 50Kb (up to, say 300Kb for a large image) if you just want the recipient to view it on his/her monitor. If they're going to be printing it out, aim for file sizes of around 500Kb (up to possibly 2Mb for a large print).
Better still, adjust the settings on your camera so that the images it produces have file sizes of around 500Kb. That's usually good enough for reasonable size prints. Then you won't even have to worry about compressing or re-sizing the files before e-mailing them as attachments.
Chris