예제 #1
0
static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop,
			              char *def_service)
{
    DELIVER_REQUEST *request = state->request;
    SMTP_ITERATOR *iter = state->iterator;
    ARGV   *sites;
    char   *dest;
    char  **cpp;
    int     non_fallback_sites;
    int     retry_plain = 0;
    DSN_BUF *why = state->why;

    /*
     * For sanity, require that at least one of INET or INET6 is enabled.
     * Otherwise, we can't look up interface information, and we can't
     * convert names or addresses.
     */
    if (inet_proto_info()->ai_family_list[0] == 0) {
	dsb_simple(why, "4.4.4", "all network protocols are disabled");
	return;
    }

    /*
     * Future proofing: do a null destination sanity check in case we allow
     * the primary destination to be a list (it could be just separators).
     */
    sites = argv_alloc(1);
    argv_add(sites, nexthop, (char *) 0);
    if (sites->argc == 0)
	msg_panic("null destination: \"%s\"", nexthop);
    non_fallback_sites = sites->argc;
    argv_split_append(sites, var_fallback_relay, CHARS_COMMA_SP);

    /*
     * Don't give up after a hard host lookup error until we have tried the
     * fallback relay servers.
     * 
     * Don't bounce mail after a host lookup problem with a relayhost or with a
     * fallback relay.
     * 
     * Don't give up after a qualifying soft error until we have tried all
     * qualifying backup mail servers.
     * 
     * All this means that error handling and error reporting depends on whether
     * the error qualifies for trying to deliver to a backup mail server, or
     * whether we're looking up a relayhost or fallback relay. The challenge
     * then is to build this into the pre-existing SMTP client without
     * getting lost in the complexity.
     */
#define IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites) \
	    (*(cpp) && (cpp) >= (sites)->argv + (non_fallback_sites))

    for (cpp = sites->argv, (state->misc_flags |= SMTP_MISC_FLAG_FIRST_NEXTHOP);
	 SMTP_RCPT_LEFT(state) > 0 && (dest = *cpp) != 0;
	 cpp++, (state->misc_flags &= ~SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
	char   *dest_buf;
	char   *domain;
	unsigned port;
	DNS_RR *addr_list;
	DNS_RR *addr;
	DNS_RR *next;
	int     addr_count;
	int     sess_count;
	SMTP_SESSION *session;
	int     lookup_mx;
	unsigned domain_best_pref;
	MAI_HOSTADDR_STR hostaddr;

	if (cpp[1] == 0)
	    state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;

	/*
	 * Parse the destination. If no TCP port is specified, use the port
	 * that is reserved for the protocol (SMTP or LMTP).
	 */
	dest_buf = smtp_parse_destination(dest, def_service, &domain, &port);
	if (var_helpful_warnings && var_smtp_tls_wrappermode == 0
	    && ntohs(port) == 465) {
	    msg_info("SMTPS wrappermode (TCP port 465) requires setting "
		     "\"%s = yes\", and \"%s = encrypt\" (or stronger)",
		     VAR_LMTP_SMTP(TLS_WRAPPER), VAR_LMTP_SMTP(TLS_LEVEL));
	}
#define NO_HOST	""				/* safety */
#define NO_ADDR	""				/* safety */

	SMTP_ITER_INIT(iter, dest, NO_HOST, NO_ADDR, port, state);

	/*
	 * Resolve an SMTP or LMTP server. In the case of SMTP, skip mail
	 * exchanger lookups when a quoted host is specified or when DNS
	 * lookups are disabled.
	 */
	if (msg_verbose)
	    msg_info("connecting to %s port %d", domain, ntohs(port));
	if (smtp_mode) {
	    if (ntohs(port) == IPPORT_SMTP)
		state->misc_flags |= SMTP_MISC_FLAG_LOOP_DETECT;
	    else
		state->misc_flags &= ~SMTP_MISC_FLAG_LOOP_DETECT;
	    lookup_mx = (smtp_dns_support != SMTP_DNS_DISABLED && *dest != '[');
	} else
	    lookup_mx = 0;
	if (!lookup_mx) {
	    addr_list = smtp_host_addr(domain, state->misc_flags, why);
	    /* XXX We could be an MX host for this destination... */
	} else {
	    int     i_am_mx = 0;

	    addr_list = smtp_domain_addr(domain, &iter->mx, state->misc_flags,
					 why, &i_am_mx);
	    /* If we're MX host, don't connect to non-MX backups. */
	    if (i_am_mx)
		state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
	}

	/*
	 * Don't try fall-back hosts if mail loops to myself. That would just
	 * make the problem worse.
	 */
	if (addr_list == 0 && SMTP_HAS_LOOP_DSN(why))
	    state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;

	/*
	 * No early loop exit or we have a memory leak with dest_buf.
	 */
	if (addr_list)
	    domain_best_pref = addr_list->pref;

	/*
	 * When session caching is enabled, store the first good session for
	 * this delivery request under the next-hop destination name. All
	 * good sessions will be stored under their specific server IP
	 * address.
	 * 
	 * XXX smtp_session_cache_destinations specifies domain names without
	 * :port, because : is already used for maptype:mapname. Because of
	 * this limitation we use the bare domain without the optional [] or
	 * non-default TCP port.
	 * 
	 * Opportunistic (a.k.a. on-demand) session caching on request by the
	 * queue manager. This is turned temporarily when a destination has a
	 * high volume of mail in the active queue. When the surge reaches
	 * its end, the queue manager requests that connections be retrieved
	 * but not stored.
	 */
	if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
	    smtp_cache_policy(state, domain);
	    if (state->misc_flags & SMTP_MISC_FLAG_CONN_CACHE_MASK)
		SET_NEXTHOP_STATE(state, dest);
	}

	/*
	 * Delete visited cached hosts from the address list.
	 * 
	 * Optionally search the connection cache by domain name or by primary
	 * MX address before we try to create new connections.
	 * 
	 * Enforce the MX session and MX address counts per next-hop or
	 * fall-back destination. smtp_reuse_session() will truncate the
	 * address list when either limit is reached.
	 */
	if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD)) {
	    if (state->cache_used->used > 0)
		smtp_scrub_addr_list(state->cache_used, &addr_list);
	    sess_count = addr_count =
		smtp_reuse_session(state, &addr_list, domain_best_pref);
	} else
	    sess_count = addr_count = 0;

	/*
	 * Connect to an SMTP server: create primary MX connections, and
	 * reuse or create backup MX connections.
	 * 
	 * At the start of an SMTP session, all recipients are unmarked. In the
	 * course of an SMTP session, recipients are marked as KEEP (deliver
	 * to alternate mail server) or DROP (remove from recipient list). At
	 * the end of an SMTP session, weed out the recipient list. Unmark
	 * any left-over recipients and try to deliver them to a backup mail
	 * server.
	 * 
	 * Cache the first good session under the next-hop destination name.
	 * Cache all good sessions under their physical endpoint.
	 * 
	 * Don't query the session cache for primary MX hosts. We already did
	 * that in smtp_reuse_session(), and if any were found in the cache,
	 * they were already deleted from the address list.
	 * 
	 * Currently, we use smtp_reuse_addr() only for SASL-unauthenticated
	 * connections. Furthermore, we rely on smtp_reuse_addr() to look up
	 * an existing SASL-unauthenticated connection only when a new
	 * connection would be guaranteed not to require SASL authentication.
	 * 
	 * In addition, we rely on smtp_reuse_addr() to look up an existing
	 * plaintext connection only when a new connection would be
	 * guaranteed not to use TLS.
	 */
	for (addr = addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) {
	    next = addr->next;
	    if (++addr_count == var_smtp_mxaddr_limit)
		next = 0;
	    if (dns_rr_to_pa(addr, &hostaddr) == 0) {
		msg_warn("cannot convert type %s record to printable address",
			 dns_strtype(addr->type));
		/* XXX Assume there is no code at the end of this loop. */
		continue;
	    }
	    vstring_strcpy(iter->addr, hostaddr.buf);
	    vstring_strcpy(iter->host, SMTP_HNAME(addr));
	    iter->rr = addr;
#ifdef USE_TLS
	    if (!smtp_tls_policy_cache_query(why, state->tls, iter)) {
		msg_warn("TLS policy lookup for %s/%s: %s",
			 STR(iter->dest), STR(iter->host), STR(why->reason));
		continue;
		/* XXX Assume there is no code at the end of this loop. */
	    }
	    if (var_smtp_tls_wrappermode
		&& state->tls->level < TLS_LEV_ENCRYPT) {
		msg_warn("%s requires \"%s = encrypt\" (or stronger)",
		      VAR_LMTP_SMTP(TLS_WRAPPER), VAR_LMTP_SMTP(TLS_LEVEL));
		continue;
		/* XXX Assume there is no code at the end of this loop. */
	    }
	    /* Disable TLS when retrying after a handshake failure */
	    if (retry_plain) {
		state->tls->level = TLS_LEV_NONE;
		retry_plain = 0;
	    }
#endif
	    if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0
		|| addr->pref == domain_best_pref
		|| !(session = smtp_reuse_addr(state,
					  SMTP_KEY_MASK_SCACHE_ENDP_LABEL)))
		session = smtp_connect_addr(iter, why, state->misc_flags);
	    if ((state->session = session) != 0) {
		session->state = state;
#ifdef USE_TLS
		session->tls_nexthop = domain;
#endif
		if (addr->pref == domain_best_pref)
		    session->features |= SMTP_FEATURE_BEST_MX;
		/* Don't count handshake errors towards the session limit. */
		if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
		    && next == 0)
		    state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
		if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0
		    && smtp_helo(state) != 0) {
#ifdef USE_TLS

		    /*
		     * When an opportunistic TLS handshake fails, try the
		     * same address again, with TLS disabled. See also the
		     * RETRY_AS_PLAINTEXT macro.
		     */
		    if ((retry_plain = session->tls_retry_plain) != 0) {
			--addr_count;
			next = addr;
		    }
#endif

		    /*
		     * When a TLS handshake fails, the stream is marked
		     * "dead" to avoid further I/O over a broken channel.
		     */
		    if (!THIS_SESSION_IS_FORBIDDEN
			&& vstream_ferror(session->stream) == 0
			&& vstream_feof(session->stream) == 0)
			smtp_quit(state);
		} else {
		    /* Do count delivery errors towards the session limit. */
		    if (++sess_count == var_smtp_mxsess_limit)
			next = 0;
		    if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
			&& next == 0)
			state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
		    smtp_xfer(state);
#ifdef USE_TLS

		    /*
		     * When opportunistic TLS fails after the STARTTLS
		     * handshake, try the same address again, with TLS
		     * disabled. See also the RETRY_AS_PLAINTEXT macro.
		     */
		    if ((retry_plain = session->tls_retry_plain) != 0) {
			--sess_count;
			--addr_count;
			next = addr;
		    }
#endif
		}
		smtp_cleanup_session(state);
	    } else {
		/* The reason already includes the IP address and TCP port. */
		msg_info("%s", STR(why->reason));
	    }
	    /* XXX Code above assumes there is no code at this loop ending. */
	}
	dns_rr_free(addr_list);
	if (iter->mx) {
	    dns_rr_free(iter->mx);
	    iter->mx = 0;			/* Just in case */
	}
	myfree(dest_buf);
	if (state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
	    break;
    }

    /*
     * We still need to deliver, bounce or defer some left-over recipients:
     * either mail loops or some backup mail server was unavailable.
     */
    if (SMTP_RCPT_LEFT(state) > 0) {

	/*
	 * In case of a "no error" indication we make up an excuse: we did
	 * find the host address, but we did not attempt to connect to it.
	 * This can happen when the fall-back relay was already tried via a
	 * cached connection, so that the address list scrubber left behind
	 * an empty list.
	 */
	if (!SMTP_HAS_DSN(why)) {
	    dsb_simple(why, "4.3.0",
		       "server unavailable or unable to receive mail");
	}

	/*
	 * Pay attention to what could be configuration problems, and pretend
	 * that these are recoverable rather than bouncing the mail.
	 */
	else if (!SMTP_HAS_SOFT_DSN(why)) {

	    /*
	     * The fall-back destination did not resolve as expected, or it
	     * is refusing to talk to us, or mail for it loops back to us.
	     */
	    if (IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites)) {
		msg_warn("%s configuration problem", VAR_SMTP_FALLBACK);
		vstring_strcpy(why->status, "4.3.5");
		/* XXX Keep the diagnostic code and MTA. */
	    }

	    /*
	     * The next-hop relayhost did not resolve as expected, or it is
	     * refusing to talk to us, or mail for it loops back to us.
	     * 
	     * XXX There is no equivalent safety net for mis-configured
	     * sender-dependent relay hosts. The trivial-rewrite resolver
	     * would have to flag the result, and the queue manager would
	     * have to provide that information to delivery agents.
	     */
	    else if (smtp_mode && strcmp(sites->argv[0], var_relayhost) == 0) {
		msg_warn("%s configuration problem", VAR_RELAYHOST);
		vstring_strcpy(why->status, "4.3.5");
		/* XXX Keep the diagnostic code and MTA. */
	    }

	    /*
	     * Mail for the next-hop destination loops back to myself. Pass
	     * the mail to the best_mx_transport or bounce it.
	     */
	    else if (smtp_mode && SMTP_HAS_LOOP_DSN(why) && *var_bestmx_transp) {
		dsb_reset(why);			/* XXX */
		state->status = deliver_pass_all(MAIL_CLASS_PRIVATE,
						 var_bestmx_transp,
						 request);
		SMTP_RCPT_LEFT(state) = 0;	/* XXX */
	    }
	}
    }

    /*
     * Cleanup.
     */
    if (HAVE_NEXTHOP_STATE(state))
	FREE_NEXTHOP_STATE(state);
    argv_free(sites);
}
예제 #2
0
static void smtp_connect_remote(SMTP_STATE *state, const char *nexthop,
				        char *def_service)
{
    DELIVER_REQUEST *request = state->request;
    ARGV   *sites;
    char   *dest;
    char  **cpp;
    int     non_fallback_sites;
    int     retry_plain = 0;
    DSN_BUF *why = state->why;

    /*
     * First try to deliver to the indicated destination, then try to deliver
     * to the optional fall-back relays.
     * 
     * Future proofing: do a null destination sanity check in case we allow the
     * primary destination to be a list (it could be just separators).
     */
    sites = argv_alloc(1);
    argv_add(sites, nexthop, (char *) 0);
    if (sites->argc == 0)
	msg_panic("null destination: \"%s\"", nexthop);
    non_fallback_sites = sites->argc;
    if ((state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0)
	argv_split_append(sites, var_fallback_relay, ", \t\r\n");

    /*
     * Don't give up after a hard host lookup error until we have tried the
     * fallback relay servers.
     * 
     * Don't bounce mail after a host lookup problem with a relayhost or with a
     * fallback relay.
     * 
     * Don't give up after a qualifying soft error until we have tried all
     * qualifying backup mail servers.
     * 
     * All this means that error handling and error reporting depends on whether
     * the error qualifies for trying to deliver to a backup mail server, or
     * whether we're looking up a relayhost or fallback relay. The challenge
     * then is to build this into the pre-existing SMTP client without
     * getting lost in the complexity.
     */
#define IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites) \
	    (*(cpp) && (cpp) >= (sites)->argv + (non_fallback_sites))

    for (cpp = sites->argv, (state->misc_flags |= SMTP_MISC_FLAG_FIRST_NEXTHOP);
	 SMTP_RCPT_LEFT(state) > 0 && (dest = *cpp) != 0;
	 cpp++, (state->misc_flags &= ~SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
	char   *dest_buf;
	char   *domain;
	unsigned port;
	DNS_RR *addr_list;
	DNS_RR *addr;
	DNS_RR *next;
	int     addr_count;
	int     sess_count;
	SMTP_SESSION *session;
	int     lookup_mx;
	unsigned domain_best_pref;
	MAI_HOSTADDR_STR hostaddr;

	if (cpp[1] == 0)
	    state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;

	/*
	 * Parse the destination. Default is to use the SMTP port. Look up
	 * the address instead of the mail exchanger when a quoted host is
	 * specified, or when DNS lookups are disabled.
	 */
	dest_buf = smtp_parse_destination(dest, def_service, &domain, &port);
	if (var_helpful_warnings && ntohs(port) == 465) {
	    msg_info("CLIENT wrappermode (port smtps/465) is unimplemented");
	    msg_info("instead, send to (port submission/587) with STARTTLS");
	}

	/*
	 * Resolve an SMTP server. Skip mail exchanger lookups when a quoted
	 * host is specified, or when DNS lookups are disabled.
	 */
	if (msg_verbose)
	    msg_info("connecting to %s port %d", domain, ntohs(port));
	if ((state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0) {
	    if (ntohs(port) == IPPORT_SMTP)
		state->misc_flags |= SMTP_MISC_FLAG_LOOP_DETECT;
	    else
		state->misc_flags &= ~SMTP_MISC_FLAG_LOOP_DETECT;
	    lookup_mx = (var_disable_dns == 0 && *dest != '[');
	} else
	    lookup_mx = 0;
	if (!lookup_mx) {
	    addr_list = smtp_host_addr(domain, state->misc_flags, why);
	    /* XXX We could be an MX host for this destination... */
	} else {
	    int     i_am_mx = 0;

	    addr_list = smtp_domain_addr(domain, state->misc_flags,
					 why, &i_am_mx);
	    /* If we're MX host, don't connect to non-MX backups. */
	    if (i_am_mx)
		state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
	}

	/*
	 * Don't try fall-back hosts if mail loops to myself. That would just
	 * make the problem worse.
	 */
	if (addr_list == 0 && SMTP_HAS_LOOP_DSN(why))
	    state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;

	/*
	 * No early loop exit or we have a memory leak with dest_buf.
	 */
	if (addr_list)
	    domain_best_pref = addr_list->pref;

	/*
	 * When session caching is enabled, store the first good session for
	 * this delivery request under the next-hop destination name. All
	 * good sessions will be stored under their specific server IP
	 * address.
	 * 
	 * XXX Replace sites->argv by (lookup_mx, domain, port) triples so we
	 * don't have to make clumsy ad-hoc copies and keep track of who
	 * free()s the memory.
	 * 
	 * XXX smtp_session_cache_destinations specifies domain names without
	 * :port, because : is already used for maptype:mapname. Because of
	 * this limitation we use the bare domain without the optional [] or
	 * non-default TCP port.
	 * 
	 * Opportunistic (a.k.a. on-demand) session caching on request by the
	 * queue manager. This is turned temporarily when a destination has a
	 * high volume of mail in the active queue.
	 * 
	 * XXX Disable connection caching when sender-dependent authentication
	 * is enabled. We must not send someone elses mail over an
	 * authenticated connection, and we must not send mail that requires
	 * authentication over a connection that wasn't authenticated.
	 */
	if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
	    smtp_cache_policy(state, domain);
	    if (state->misc_flags & SMTP_MISC_FLAG_CONN_STORE)
		SET_NEXTHOP_STATE(state, lookup_mx, domain, port);
	}

	/*
	 * Delete visited cached hosts from the address list.
	 * 
	 * Optionally search the connection cache by domain name or by primary
	 * MX address before we try to create new connections.
	 * 
	 * Enforce the MX session and MX address counts per next-hop or
	 * fall-back destination. smtp_reuse_session() will truncate the
	 * address list when either limit is reached.
	 */
	if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD)) {
	    if (state->cache_used->used > 0)
		smtp_scrub_addr_list(state->cache_used, &addr_list);
	    sess_count = addr_count =
		smtp_reuse_session(state, lookup_mx, domain, port,
				   &addr_list, domain_best_pref);
	} else
	    sess_count = addr_count = 0;

	/*
	 * Connect to an SMTP server: create primary MX connections, and
	 * reuse or create backup MX connections.
	 * 
	 * At the start of an SMTP session, all recipients are unmarked. In the
	 * course of an SMTP session, recipients are marked as KEEP (deliver
	 * to alternate mail server) or DROP (remove from recipient list). At
	 * the end of an SMTP session, weed out the recipient list. Unmark
	 * any left-over recipients and try to deliver them to a backup mail
	 * server.
	 * 
	 * Cache the first good session under the next-hop destination name.
	 * Cache all good sessions under their physical endpoint.
	 * 
	 * Don't query the session cache for primary MX hosts. We already did
	 * that in smtp_reuse_session(), and if any were found in the cache,
	 * they were already deleted from the address list.
	 */
	for (addr = addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) {
	    next = addr->next;
	    if (++addr_count == var_smtp_mxaddr_limit)
		next = 0;
	    if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0
		|| addr->pref == domain_best_pref
		|| dns_rr_to_pa(addr, &hostaddr) == 0
		|| !(session = smtp_reuse_addr(state, hostaddr.buf, port)))
		session = smtp_connect_addr(dest, addr, port, why,
					    state->misc_flags);
	    if ((state->session = session) != 0) {
		session->state = state;
		if (addr->pref == domain_best_pref)
		    session->features |= SMTP_FEATURE_BEST_MX;
		/* Don't count handshake errors towards the session limit. */
		if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
		    && next == 0)
		    state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
#ifdef USE_TLS
		/* Disable TLS when retrying after a handshake failure */
		if (retry_plain) {
		    if (session->tls_level >= TLS_LEV_ENCRYPT)
			msg_panic("Plain-text retry wrong for mandatory TLS");
		    session->tls_level = TLS_LEV_NONE;
		    retry_plain = 0;
		}
		session->tls_nexthop = domain;	/* for TLS_LEV_SECURE */
#endif
		if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0
		    && smtp_helo(state) != 0) {
#ifdef USE_TLS

		    /*
		     * When an opportunistic TLS handshake fails, try the
		     * same address again, with TLS disabled. See also the
		     * RETRY_AS_PLAINTEXT macro.
		     */
		    if ((retry_plain = session->tls_retry_plain) != 0) {
			--addr_count;
			next = addr;
		    }
#endif

		    /*
		     * When a TLS handshake fails, the stream is marked
		     * "dead" to avoid further I/O over a broken channel.
		     */
		    if (!THIS_SESSION_IS_DEAD
			&& vstream_ferror(session->stream) == 0
			&& vstream_feof(session->stream) == 0)
			smtp_quit(state);
		} else {
		    /* Do count delivery errors towards the session limit. */
		    if (++sess_count == var_smtp_mxsess_limit)
			next = 0;
		    if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
			&& next == 0)
			state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
		    smtp_xfer(state);
		}
		smtp_cleanup_session(state);
	    } else {
		/* The reason already includes the IP address and TCP port. */
		msg_info("%s", STR(why->reason));
	    }
	    /* Insert: test if we must skip the remaining MX hosts. */
	}
	dns_rr_free(addr_list);
	myfree(dest_buf);
	if (state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
	    break;
    }

    /*
     * We still need to deliver, bounce or defer some left-over recipients:
     * either mail loops or some backup mail server was unavailable.
     */
    if (SMTP_RCPT_LEFT(state) > 0) {

	/*
	 * In case of a "no error" indication we make up an excuse: we did
	 * find the host address, but we did not attempt to connect to it.
	 * This can happen when the fall-back relay was already tried via a
	 * cached connection, so that the address list scrubber left behind
	 * an empty list.
	 */
	if (!SMTP_HAS_DSN(why)) {
	    dsb_simple(why, "4.3.0",
		       "server unavailable or unable to receive mail");
	}

	/*
	 * Pay attention to what could be configuration problems, and pretend
	 * that these are recoverable rather than bouncing the mail.
	 */
	else if (!SMTP_HAS_SOFT_DSN(why)
		 && (state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0) {

	    /*
	     * The fall-back destination did not resolve as expected, or it
	     * is refusing to talk to us, or mail for it loops back to us.
	     */
	    if (IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites)) {
		msg_warn("%s configuration problem", VAR_SMTP_FALLBACK);
		vstring_strcpy(why->status, "4.3.5");
		/* XXX Keep the diagnostic code and MTA. */
	    }

	    /*
	     * The next-hop relayhost did not resolve as expected, or it is
	     * refusing to talk to us, or mail for it loops back to us.
	     */
	    else if (strcmp(sites->argv[0], var_relayhost) == 0) {
		msg_warn("%s configuration problem", VAR_RELAYHOST);
		vstring_strcpy(why->status, "4.3.5");
		/* XXX Keep the diagnostic code and MTA. */
	    }

	    /*
	     * Mail for the next-hop destination loops back to myself. Pass
	     * the mail to the best_mx_transport or bounce it.
	     */
	    else if (SMTP_HAS_LOOP_DSN(why) && *var_bestmx_transp) {
		dsb_reset(why);			/* XXX */
		state->status = deliver_pass_all(MAIL_CLASS_PRIVATE,
						 var_bestmx_transp,
						 request);
		SMTP_RCPT_LEFT(state) = 0;	/* XXX */
	    }
	}
    }

    /*
     * Cleanup.
     */
    if (HAVE_NEXTHOP_STATE(state))
	FREE_NEXTHOP_STATE(state);
    argv_free(sites);
}