function isRightEmail(str)
	if string.len(str or "") < 6 then return false end
	local b,e = string.find(str or "", '@')
	local bstr = ""
	local estr = ""
	if b then
	 bstr = string.sub(str, 1, b-1)
	 estr = string.sub(str, e+1, -1)
	else
	 return false
	end


	-- check the string before '@'
	local p1,p2 = string.find(bstr, "[%w_]+")
	if (p1 ~= 1) or (p2 ~= string.len(bstr)) then return false end


	-- check the string after '@'
	if string.find(estr, "^[%.]+") then return false end
	if string.find(estr, "%.[%.]+") then return false end
	if string.find(estr, "@") then return false end
	if string.find(estr, "[%.]+$") then return false end


	_,count = string.gsub(estr, "%.", "")
	if (count < 1 ) or (count > 3) then
	 return false
	end


	return true
end