+ const char *to_headers[] = {"Envelope-to", "X-Original-To"};
+
+ primary = notmuch_config_get_user_primary_email (config);
+ other = notmuch_config_get_user_other_email (config, &other_len);
+
+ /* sadly, there is no standard way to find out to which email
+ * address a mail was delivered - what is in the headers depends
+ * on the MTAs used along the way. So we are trying a number of
+ * heuristics which hopefully will answer this question.
+
+ * We only got here if none of the users email addresses are in
+ * the To: or Cc: header. From here we try the following in order:
+ * 1) check for an Envelope-to: header
+ * 2) check for an X-Original-To: header
+ * 3) check for a (for <email@add.res>) clause in Received: headers
+ * 4) check for the domain part of known email addresses in the
+ * 'by' part of Received headers
+ * If none of these work, we give up and return NULL
+ */
+ for (i = 0; i < sizeof(to_headers)/sizeof(*to_headers); i++) {
+ tohdr = xstrdup(notmuch_message_get_header (message, to_headers[i]));
+ if (tohdr && *tohdr) {
+ /* tohdr is potentialy a list of email addresses, so here we
+ * check if one of the email addresses is a substring of tohdr
+ */
+ if (strcasestr(tohdr, primary)) {
+ free(tohdr);
+ return primary;
+ }
+ for (j = 0; j < other_len; j++)
+ if (strcasestr (tohdr, other[j])) {
+ free(tohdr);
+ return other[j];
+ }
+ free(tohdr);
+ }
+ }
+
+ /* We get the concatenated Received: headers and search from the
+ * front (last Received: header added) and try to extract from
+ * them indications to which email address this message was
+ * delivered.
+ * The Received: header is special in our get_header function
+ * and is always concated.
+ */