diff --git a/zuul/lib/connections.py b/zuul/lib/connections.py
index 92ddb0f..6159bfc 100644
--- a/zuul/lib/connections.py
+++ b/zuul/lib/connections.py
@@ -12,6 +12,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import logging
 import re
 
 import zuul.connection.gerrit
@@ -19,6 +20,7 @@
 
 
 def configure_connections(config):
+    log = logging.getLogger("configure_connections")
     # Register connections from the config
 
     # TODO(jhesketh): import connection modules dynamically
@@ -54,13 +56,21 @@
     # connection named 'gerrit' or 'smtp' respectfully
 
     if 'gerrit' in config.sections():
-        connections['gerrit'] = \
-            zuul.connection.gerrit.GerritConnection(
-                'gerrit', dict(config.items('gerrit')))
+        if 'gerrit' in connections:
+            log.warning("The legacy [gerrit] section will be ignored in favour"
+                        " of the [connection gerrit].")
+        else:
+            connections['gerrit'] = \
+                zuul.connection.gerrit.GerritConnection(
+                    'gerrit', dict(config.items('gerrit')))
 
     if 'smtp' in config.sections():
-        connections['smtp'] = \
-            zuul.connection.smtp.SMTPConnection(
-                'smtp', dict(config.items('smtp')))
+        if 'smtp' in connections:
+            log.warning("The legacy [smtp] section will be ignored in favour"
+                        " of the [connection smtp].")
+        else:
+            connections['smtp'] = \
+                zuul.connection.smtp.SMTPConnection(
+                    'smtp', dict(config.items('smtp')))
 
     return connections