You can use this to import smtplib:
import clr
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *
import sys
pyt_path = r'C:\Program Files (x86)\IronPython 2.7\Lib'
sys.path.append(pyt_path)
import System
import smtplib
#The inputs to this node will be stored as a list in the IN variables.
dataEnteringNode = IN
#Assign your output to the OUT variable.
OUT = dir(smtplib)