[csense]

Those regular expressions desperately need refactored. Maybe like this:

   c = r"[-!#$%&'*+/=?^_`{}|~0-9A-Z]"
   dot_atom = r"{c}+(\.{c}+)*".format(c=c)

   c1 = r"[\001-\010\013\014\016-\037!#-\[\]-\177]"
   c2 = r"[\001-\011\013\014\016-\177]"
   quoted_string = r"'({c1}|\\{c2})*'".format(c1=c1, c2=c2)

   c = r"[A-Z0-9]"
   dash_something = r"(?:-*{c}+)".format(c=c)
   domain = r"(?:{c}+{dash_something}\.)+{c}{{2,6}}".format(c=c, dash_something=dash_something)

   email = "^({dot_atom}|{quoted_string})@{domain}$"

There's a typo in the original, which I fixed: \001-011 should be \001-\011.