+ return n;
+}
+
+/* Does the address in the Reply-To header of 'message' already appear
+ * in either the 'To' or 'Cc' header of the message?
+ */
+static notmuch_bool_t
+reply_to_header_is_redundant (GMimeMessage *message,
+ InternetAddressList *reply_to_list)
+{
+ const char *addr, *reply_to;
+ InternetAddress *address;
+ InternetAddressMailbox *mailbox;
+ InternetAddressList *recipients;
+ notmuch_bool_t ret = FALSE;
+ int i;
+
+ if (reply_to_list == NULL ||
+ internet_address_list_length (reply_to_list) != 1)
+ return 0;
+
+ address = internet_address_list_get_address (reply_to_list, 0);
+ if (INTERNET_ADDRESS_IS_GROUP (address))
+ return 0;
+
+ mailbox = INTERNET_ADDRESS_MAILBOX (address);
+ reply_to = internet_address_mailbox_get_addr (mailbox);
+
+ recipients = g_mime_message_get_all_recipients (message);
+
+ for (i = 0; i < internet_address_list_length (recipients); i++) {
+ address = internet_address_list_get_address (recipients, i);
+ if (INTERNET_ADDRESS_IS_GROUP (address))
+ continue;
+
+ mailbox = INTERNET_ADDRESS_MAILBOX (address);
+ addr = internet_address_mailbox_get_addr (mailbox);
+ if (strcmp (addr, reply_to) == 0) {
+ ret = TRUE;
+ break;
+ }
+ }
+
+ g_object_unref (G_OBJECT (recipients));
+
+ return ret;
+}
+
+static InternetAddressList *get_sender(GMimeMessage *message)
+{
+ const char *reply_to;
+
+ reply_to = g_mime_message_get_reply_to (message);
+ if (reply_to && *reply_to) {
+ InternetAddressList *reply_to_list;
+
+ /*
+ * Some mailing lists munge the Reply-To header despite it
+ * being A Bad Thing, see
+ * http://marc.merlins.org/netrants/reply-to-harmful.html
+ *
+ * The munging is easy to detect, because it results in a
+ * redundant reply-to header, (with an address that already
+ * exists in either To or Cc). So in this case, we ignore the
+ * Reply-To field and use the From header. This ensures the
+ * original sender will get the reply even if not subscribed
+ * to the list. Note that the address in the Reply-To header
+ * will always appear in the reply if reply_all is true.
+ */
+ reply_to_list = internet_address_list_parse_string (reply_to);
+ if (! reply_to_header_is_redundant (message, reply_to_list))
+ return reply_to_list;
+
+ g_object_unref (G_OBJECT (reply_to_list));
+ }
+
+ return internet_address_list_parse_string (
+ g_mime_message_get_sender (message));
+}
+
+static InternetAddressList *get_to(GMimeMessage *message)
+{
+ return g_mime_message_get_recipients (message, GMIME_RECIPIENT_TYPE_TO);
+}
+
+static InternetAddressList *get_cc(GMimeMessage *message)
+{
+ return g_mime_message_get_recipients (message, GMIME_RECIPIENT_TYPE_CC);
+}
+
+static InternetAddressList *get_bcc(GMimeMessage *message)
+{
+ return g_mime_message_get_recipients (message, GMIME_RECIPIENT_TYPE_BCC);
+}
+
+/* Augment the recipients of 'reply' from the "Reply-to:", "From:",
+ * "To:", "Cc:", and "Bcc:" headers of 'message'.
+ *
+ * If 'reply_all' is true, use sender and all recipients, otherwise
+ * scan the headers for the first that contains something other than
+ * the user's addresses and add the recipients from this header
+ * (typically this would be reply-to-sender, but also handles reply to
+ * user's own message in a sensible way).
+ *
+ * If any of the user's addresses were found in these headers, the
+ * first of these returned, otherwise NULL is returned.
+ */
+static const char *
+add_recipients_from_message (GMimeMessage *reply,
+ notmuch_config_t *config,
+ GMimeMessage *message,
+ notmuch_bool_t reply_all)
+{
+ struct {
+ InternetAddressList * (*get_header)(GMimeMessage *message);
+ GMimeRecipientType recipient_type;
+ } reply_to_map[] = {
+ { get_sender, GMIME_RECIPIENT_TYPE_TO },
+ { get_to, GMIME_RECIPIENT_TYPE_TO },
+ { get_cc, GMIME_RECIPIENT_TYPE_CC },
+ { get_bcc, GMIME_RECIPIENT_TYPE_BCC },