commit 821df54dc3b3e977e3c55812b1d9dd8587078cd5
Author: Rick Liu <rickliu@fortinet.com>
Date:   Thu Nov 24 16:34:29 2016 -0800

    Fix ticket 4438: email header is too large for big file changesets

diff --git a/reviewboard/notifications/email.py b/reviewboard/notifications/email.py
index 761e826543ae2016999f22b63c3ad7719ca8a1c5..62d23ca3b6bb8086befbb1884e542300b10371b4 100644
--- a/reviewboard/notifications/email.py
+++ b/reviewboard/notifications/email.py
@@ -599,9 +599,6 @@ def send_review_mail(user, review_request, subject, in_reply_to,
             if filediff.is_new or filediff.copied or filediff.moved:
                 modified_files.add(filediff.dest_file)
 
-        for filename in modified_files:
-            headers.appendlist('X-ReviewBoard-Diff-For', filename)
-
     subject = subject.strip()
     to_field = list(to_field)
     cc_field = list(cc_field)