This usually happens if .jpg images were saved in CMYK format instead of RGB format. If you load the image into your image editing software and resave the image in RBG format, the Add Graphic Image command will work.
Graphic images for email should be in web format, which is an RBG image saved at 72 or 96dpi (screen resolution) in .jpg, .gif or .png format.
Do not use CMYK images, which is a print format. Do not use .eps or .tiff formats or native image editor formats.
The standard PoliteMail template and banner width is 640 pixels, which enables printing from email on most 8.5×11 or A size papers.