In the default shortcuts of Xfce4 there is commands affected to the following shortcut: "XF86Mail" and "XF86WWW".
What do they correspond to ?
They correspond to dedicated keys available on some keyboards, typically in a cluster of “multimedia” keys (see for example this Microsoft keyboard with “email and internet hot keys”);
XF86Mail is the key assigned to access email,
XF86WWW the key assigned to start a web browser.
Taking a look at the source code of file
XF86keysym.h, and this table it seems to be exactly what the name suppose to be in a very suggestive way: The keyboard symbols to "Mail" and "Internet"(some of them have the "E" of Internet Explorer printed on it):
#define XF86XK_Mail 0x1008FF19 /* Invoke user's mail program */ #define XF86XK_WWW 0x1008FF2E /* Invoke web browser */