The GIMP Useless Mail Plugin. Basically, it's a plugin that E-mails the image. Uses MIME.

It's generally much easier to just use your favorite MUA, or place the image in shared directory or web page, though, but this is sometimes convinient.

In GIMP 1.0, GUMP can't be scripted. Thus it's a bit harder to use fierysteel.scm for flaming.