Open
the image in Photoshop, and choose File > Save For Web
& Devices.
Click the Optimized tab at the top of the Save For Web
& Devices dialog box.
Choose JPEG Low from the Preset menu.
Click the Image Size tab.
Make sure that Constrain Proportions is selected and
enter a width. For e‑mail, 400 pixels is a good size. Use a smaller
size if your recipient has a slow Internet connection.
Click Save. Enter a file name and location in which to
save the file. Under Format, make sure that Images Only is selected.
Click Save.
Now you are ready to e‑mail the file. In some e‑mail programs,
you can drag the file into the body of the message. In other programs,
you use the Attach or Insert command.