diff -r 59de7ad827e2 roundup/roundupdb.py
--- a/roundup/roundupdb.py	Tue May 15 12:38:36 2012 +0200
+++ b/roundup/roundupdb.py	Tue May 15 19:04:55 2012 -0400
@@ -35,6 +35,7 @@
 from anypy.email_ import FeedParser
 
 from roundup import password, date, hyperdb
+from roundup.configuration import NODEFAULT
 from roundup.i18n import _
 from roundup.hyperdb import iter_roles
 
@@ -621,23 +622,32 @@
         '''
         # simplistic check to see if the url is valid,
         # then append a trailing slash if it is missing
+        lines = []
+
+        # ensure the email address is properly quoted
+        email = formataddr((self.db.config.TRACKER_NAME,
+            self.db.config.TRACKER_EMAIL))
+        lines.append(email)
+
         base = self.db.config.TRACKER_WEB
-        if (not isinstance(base , type('')) or
-            not (base.startswith('http://') or base.startswith('https://'))):
+        if base in [NODEFAULT, None]:
+            web = None
+        elif (not isinstance(base , type('')) or
+              not (base.startswith('http://') or base.startswith('https://'))):
             web = "Configuration Error: TRACKER_WEB isn't a " \
                 "fully-qualified URL"
         else:
             if not base.endswith('/'):
                 base = base + '/'
             web = base + self.classname + issueid
+        if web:
+            lines.append('<%s>' % web)
 
-        # ensure the email address is properly quoted
-        email = formataddr((self.db.config.TRACKER_NAME,
-            self.db.config.TRACKER_EMAIL))
-
-        line = '_' * max(len(web)+2, len(email))
-        return '\n%s\n%s\n<%s>\n%s'%(line, email, web, line)
-
+        maxlinelen = max(len(x) for x in lines)
+        line = '_' * maxlinelen
+        lines.insert(0, line)
+        lines.append(line)
+        return '\n' + '\n'.join(lines)
 
     def generateCreateNote(self, issueid):
         """Generate a create note that lists initial property values
diff -r 59de7ad827e2 test/test_mailgw.py
--- a/test/test_mailgw.py	Tue May 15 12:38:36 2012 +0200
+++ b/test/test_mailgw.py	Tue May 15 19:04:55 2012 -0400
@@ -1065,6 +1065,51 @@
                 self.assertEqual(f.content, content [n])
         self.assertEqual(msg.content, 'First part: Text')
 
+    def testNODEFAULTWebSignature(self):
+        self.doNewIssue()
+        self.instance.config['TRACKER_WEB'] = None
+        message = '''Content-Type: text/plain;
+  charset="iso-8859-1"
+From: mary <mary@test.test>
+To: issue_tracker@your.tracker.email.domain.example
+Message-Id: <followup_dummy_id>
+In-Reply-To: <dummy_test_message_id>
+Subject: [issue1] Testing...
+
+This is a second followup
+'''
+        self._handle_mail(message, trap_exc=1)
+        assert os.path.exists(SENDMAILDEBUG)
+        self.compareMessages(self._get_mail(),
+'''FROM: roundup-admin@your.tracker.email.domain.example
+TO: chef@bork.bork.bork, richard@test.test
+Content-Type: text/plain; charset="utf-8"
+Subject: [issue1] Testing...
+To: chef@bork.bork.bork, richard@test.test
+From: "Contrary, Mary" <issue_tracker@your.tracker.email.domain.example>
+Reply-To: Roundup issue tracker
+ <issue_tracker@your.tracker.email.domain.example>
+MIME-Version: 1.0
+Message-Id: <followup_dummy_id>
+In-Reply-To: <dummy_test_message_id>
+X-Roundup-Name: Roundup issue tracker
+X-Roundup-Loop: hello
+X-Roundup-Issue-Status: chatting
+Content-Transfer-Encoding: quoted-printable
+
+
+Contrary, Mary <mary@test.test> added the comment:
+
+This is a second followup
+
+----------
+status: unread -> chatting
+
+_______________________________________________________________________
+Roundup issue tracker <issue_tracker@your.tracker.email.domain.example>
+_______________________________________________________________________
+''')
+
     def testSimpleFollowup(self):
         self.doNewIssue()
         self._handle_mail('''Content-Type: text/plain;