diff --git a/validate_email.py b/validate_email.py
index 3dc50e9..fd9168e 100644
--- a/validate_email.py
+++ b/validate_email.py
@@ -51,7 +51,7 @@ except (ImportError, AttributeError):
 # even when it's not strictly necessary.  This way we don't forget
 # when it is necessary.)
 #
-WSP = r'[ \t]'                                       # see 2.2.2. Structured Header Field Bodies
+WSP = r'[\s]'                                        # see 2.2.2. Structured Header Field Bodies
 CRLF = r'(?:\r\n)'                                   # see 2.2.3. Long Header Fields
 NO_WS_CTL = r'\x01-\x08\x0b\x0c\x0f-\x1f\x7f'        # see 3.2.1. Primitive Tokens
 QUOTED_PAIR = r'(?:\\.)'                             # see 3.2.2. Quoted characters
@@ -101,7 +101,7 @@ def get_mx_ip(hostname):
         try:
             MX_DNS_CACHE[hostname] = DNS.mxlookup(hostname)
         except ServerError as e:
-            if e.rcode == 3:  # NXDOMAIN (Non-Existent Domain)
+	     if e.rcode == 3 or e.rcode == 2:  # NXDOMAIN (Non-Existent Domain) or SERVFAIL
                 MX_DNS_CACHE[hostname] = None
             else:
                 raise