diff --git a/orchestra/contrib/mailer/engine.py b/orchestra/contrib/mailer/engine.py
index 76697083..752c5a2b 100644
--- a/orchestra/contrib/mailer/engine.py
+++ b/orchestra/contrib/mailer/engine.py
@@ -7,18 +7,19 @@ from django.db.models import Q
 from django.utils import timezone
 from django.utils.encoding import smart_str
 
-from orchestra.utils.sys import LockFile
+from orchestra.utils.sys import LockFile, OperationLocked
 
 from . import settings
 from .models import Message
 
 
-def send_message(message, num=0, connection=None, bulk=100):
+def send_message(message, num=0, connection=None, bulk=settings.MAILER_BULK_MESSAGES):
     if num >= bulk and connection is not None:
         connection.close()
         connection = None
     if connection is None:
-        # Reset connection with django 
+        # Reset connection with django
+        num = 0
         connection = get_connection(backend='django.core.mail.backends.smtp.EmailBackend')
         connection.open()
     error = None
@@ -34,19 +35,22 @@ def send_message(message, num=0, connection=None, bulk=100):
     message.log(error)
 
 
-def send_pending(bulk=100):
-    with LockFile('/dev/shm/mailer.send_pending.lock'):
-        connection = None
-        num = 0
-        for message in Message.objects.filter(state=Message.QUEUED).order_by('priority'):
-            send_message(message, num, connection, bulk)
-            num += 1
-        now = timezone.now()
-        qs = Q()
-        for retries, seconds in enumerate(settings.MAILER_DEFERE_SECONDS):
-            delta = timedelta(seconds=seconds)
-            qs = qs | Q(retries=retries, last_retry__lte=now-delta)
-        for message in Message.objects.filter(state=Message.DEFERRED).filter(qs).order_by('priority'):
-            send_message(message, num, connection, bulk)
-        if connection is not None:
-            connection.close()
+def send_pending(bulk=settings.MAILER_BULK_MESSAGES):
+    try:
+        with LockFile('/dev/shm/mailer.send_pending.lock'):
+            connection = None
+            num = 0
+            for message in Message.objects.filter(state=Message.QUEUED).order_by('priority'):
+                send_message(message, num, connection, bulk)
+                num += 1
+            now = timezone.now()
+            qs = Q()
+            for retries, seconds in enumerate(settings.MAILER_DEFERE_SECONDS):
+                delta = timedelta(seconds=seconds)
+                qs = qs | Q(retries=retries, last_retry__lte=now-delta)
+            for message in Message.objects.filter(state=Message.DEFERRED).filter(qs).order_by('priority'):
+                send_message(message, num, connection, bulk)
+            if connection is not None:
+                connection.close()
+    except OperationLocked:
+        pass
diff --git a/orchestra/contrib/mailer/settings.py b/orchestra/contrib/mailer/settings.py
index 2711cbb5..0cd6da8a 100644
--- a/orchestra/contrib/mailer/settings.py
+++ b/orchestra/contrib/mailer/settings.py
@@ -17,3 +17,8 @@ MAILER_NON_QUEUED_PER_REQUEST_THRESHOLD = Setting('MAILER_NON_QUEUED_PER_REQUEST
     2,
     help_text=_("Number of emails that will be sent immediately before starting to queue them."),
 )
+
+
+MAILER_BULK_MESSAGES = Setting('MAILER_BULK_MESSAGES',
+    500,
+)