я обычно делаю так:

^ifdef[^form[email];
	^ifdef[^match[\.\.;;^form[email]];;
		^ifdef[^match[^^[-a-z0-9\._]+\@[-a-z0-9\._]+\.[a-z]{2,3}$$;i;^form[email]];
			^var[validEmail;true]
		]
	]
]