Table 2.

Description of the email spam dataset and 20 newsgroups datasets [12].

	Source domains (N S)	Target domains (N S)
Email spam	User 1 (2500)	Public set (4000)
	User 2 (2500)
	User 3 (2500)
rec versus sci	rec.autos and sci.crypt (1976)	rec.sport.hockey and sci.space (1982)
	rec.motorcycles and sci.electronics (1977)
	rec.sport.baseball and sci.med (1978)
comp versus rec	comp.graphics and rec.autos (1957)	comp.sys.mac.hardware and rec.sport.hockey (1955)
	comp.os.ms-windows.misc and rec.motorcycles (1956)
	comp.sys.ibm.pc.hardware and rec.sport.baseball (1970)
sci versus comp	sci.crypt and comp.graphics (1959)	sci.space and comp.sys.mac.hardware (1943)
	sci.electronics and comp.os.ms-windows.misc (1947)
	sci.med andcomp.sys.ibm.pc.hardware (1966)