diff --git a/reviewboard/notifications/email.py b/reviewboard/notifications/email.py
index 8a9ef745066516b71987ca08a7ceef0844a67aa9..a9382ce8806ac4b7ba0883294b7169d326f274bc 100644
--- a/reviewboard/notifications/email.py
+++ b/reviewboard/notifications/email.py
@@ -208,6 +208,10 @@ def send_review_mail(user, review_request, subject, in_reply_to,
             # two are not equal.
             sender = None
 
+
+    if hasattr(settings, 'EMAIL_TAG'):
+        subject = settings.EMAIL_TAG + subject
+
     message = SpiffyEmailMessage(subject.strip(), text_body, html_body,
                                  from_email, sender, list(to_field),
                                  list(cc_field), in_reply_to, headers)
diff --git a/reviewboard/settings.py b/reviewboard/settings.py
index ff7d793967ce45378d116717155144dc72b1f9e1..50b90cc52d604a438d001cf1406079605fd57961 100644
--- a/reviewboard/settings.py
+++ b/reviewboard/settings.py
@@ -196,3 +196,7 @@ SESSION_COOKIE_PATH = SITE_ROOT
 MEDIA_SERIAL_DIRS = ["admin", "djblets", "rb"]
 
 TEST_PACKAGES = ['reviewboard']
+
+# A tag that is prepended to each mail subject.
+# Example: '[RB] ' -> [RB] Review Request: Fixed time zone bug in flux capacitor
+EMAIL_TAG = ''