diff --git a/django/core/mail.py b/django/core/mail.py
index a5af6e610f..cc99659adb 100644
--- a/django/core/mail.py
+++ b/django/core/mail.py
@@ -8,7 +8,18 @@ import socket
 import time
 import random
 
-DNS_NAME = socket.getfqdn() # Cache the hostname
+# Cache the hostname, but do it lazily: socket.getfqdn() can take a couple of
+# seconds, which slows down the restart of the server.
+class CachedDnsName(object):
+    def __str__(self):
+        return self.get_fqdn()
+
+    def get_fqdn(self):
+        if not hasattr(self, '_fqdn'):
+            self._fqdn = socket.getfqdn()
+        return self._fqdn
+
+DNS_NAME = CachedDnsName()
 
 class BadHeaderError(ValueError):
     pass