X-Face

An X-Face is a small bitmap (48 × 48 pixels, black and white) image which is added to a Usenet posting or e-mail message, typically showing a picture of the author's face.

While many programs support X-Face, most of them are free software and based on Unix or its variations, such as KMail or Sylpheed.

The most common email programs though, as used in business and most domestic environments, do not handle X-Face natively, and the information is silently ignored.

Even where Unix is widely used (university and research environments), it has never been adopted to maximum potential (for example, by searching for senders by X-Face).

X-Image-URL accepts http or (anonymous) ftp to download the picture; typical size 64x64 pixels.