diff --git a/hc/lib/emails.py b/hc/lib/emails.py
index fcbd0da2..04c44be1 100644
--- a/hc/lib/emails.py
+++ b/hc/lib/emails.py
@@ -1,4 +1,4 @@
-import smtplib
+from smtplib import SMTPServerDisconnected, SMTPDataError
 from threading import Thread
 import time
 
@@ -22,7 +22,7 @@ class EmailThread(Thread):
                 self.message.send()
                 # No exception--great! Return from the retry loop
                 return
-            except smtplib.SMTPServerDisconnected as e:
+            except (SMTPServerDisconnected, SMTPDataError) as e:
                 if attempt + 1 == self.MAX_TRIES:
                     # This was the last attempt and it failed:
                     # re-raise the exception
diff --git a/hc/lib/tests/test_emails.py b/hc/lib/tests/test_emails.py
index a0c5387d..cffc8ba1 100644
--- a/hc/lib/tests/test_emails.py
+++ b/hc/lib/tests/test_emails.py
@@ -1,4 +1,4 @@
-from smtplib import SMTPServerDisconnected
+from smtplib import SMTPServerDisconnected, SMTPDataError
 from unittest.mock import Mock, patch
 
 from django.test import TestCase
@@ -25,3 +25,12 @@ class EmailsTestCase(TestCase):
             t.run()
 
         self.assertEqual(mock_msg.send.call_count, 3)
+
+    def test_it_retries_smtp_data_error(self, mock_time):
+        mock_msg = Mock()
+        mock_msg.send = Mock(side_effect=[SMTPDataError(454, "hello"), None])
+
+        t = EmailThread(mock_msg)
+        t.run()
+
+        self.assertEqual(mock_msg.send.call_count, 2)