Index: trac/attachment.py
===================================================================
--- trac/attachment.py	(revision 6106)
+++ trac/attachment.py	(working copy)
@@ -33,6 +33,8 @@
 from trac.env import IEnvironmentSetupParticipant
 from trac.perm import PermissionError, PermissionSystem, IPermissionPolicy
 from trac.mimeview import *
+from trac.ticket import Ticket
+from trac.ticket.notification import TicketNotifyEmail
 from trac.timeline.api import TimelineEvent
 from trac.util import get_reporter_id, create_unique_file, content_disposition
 from trac.util.datefmt import to_timestamp, utc
@@ -551,6 +553,15 @@
                 pass # don't worry if there's nothing to replace
             attachment.filename = None
         attachment.insert(filename, upload.file, size)
+        if attachment.parent_realm == 'ticket':
+            try:
+                tn = TicketNotifyEmail(self.env)
+                # have to get the ticket that the attachment will modify
+                ticket = Ticket(self.env, tkt_id=attachment.parent_id)
+                tn.notify(ticket, newticket=False, modtime=attachment.time)
+            except Exception, e:
+                self.log.exception("Failure sending notification for attachment "
+                                   "on ticket #%s: %s" % (ticket.id, e))
 
         # Redirect the user to list of attachments (must add a trailing '/')
         req.redirect(context.resource_href('..') + '/')