new file mode 100644
--- /dev/null
+++ b/src/mail/ngx_mail_proxy_module.c
@@ -0,0 +1,994 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+#include <ngx_event_connect.h>
+#include <ngx_mail.h>
+
+
+typedef struct {
+    ngx_flag_t  enable;
+    ngx_flag_t  pass_error_message;
+    ngx_flag_t  xclient;
+    size_t      buffer_size;
+    ngx_msec_t  timeout;
+} ngx_mail_proxy_conf_t;
+
+
+static void ngx_mail_proxy_block_read(ngx_event_t *rev);
+static void ngx_mail_proxy_pop3_handler(ngx_event_t *rev);
+static void ngx_mail_proxy_imap_handler(ngx_event_t *rev);
+static void ngx_mail_proxy_smtp_handler(ngx_event_t *rev);
+static void ngx_mail_proxy_dummy_handler(ngx_event_t *ev);
+static ngx_int_t ngx_mail_proxy_read_response(ngx_mail_session_t *s,
+    ngx_uint_t state);
+static void ngx_mail_proxy_handler(ngx_event_t *ev);
+static void ngx_mail_proxy_upstream_error(ngx_mail_session_t *s);
+static void ngx_mail_proxy_internal_server_error(ngx_mail_session_t *s);
+static void ngx_mail_proxy_close_session(ngx_mail_session_t *s);
+static void *ngx_mail_proxy_create_conf(ngx_conf_t *cf);
+static char *ngx_mail_proxy_merge_conf(ngx_conf_t *cf, void *parent,
+    void *child);
+
+
+static ngx_command_t  ngx_mail_proxy_commands[] = {
+
+    { ngx_string("proxy"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_proxy_conf_t, enable),
+      NULL },
+
+    { ngx_string("proxy_buffer"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_size_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_proxy_conf_t, buffer_size),
+      NULL },
+
+    { ngx_string("proxy_timeout"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_msec_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_proxy_conf_t, timeout),
+      NULL },
+
+    { ngx_string("proxy_pass_error_message"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_flag_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_proxy_conf_t, pass_error_message),
+      NULL },
+
+    { ngx_string("xclient"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_proxy_conf_t, xclient),
+      NULL },
+
+      ngx_null_command
+};
+
+
+static ngx_mail_module_t  ngx_mail_proxy_module_ctx = {
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    ngx_mail_proxy_create_conf,            /* create server configuration */
+    ngx_mail_proxy_merge_conf              /* merge server configuration */
+};
+
+
+ngx_module_t  ngx_mail_proxy_module = {
+    NGX_MODULE_V1,
+    &ngx_mail_proxy_module_ctx,            /* module context */
+    ngx_mail_proxy_commands,               /* module directives */
+    NGX_MAIL_MODULE,                       /* module type */
+    NULL,                                  /* init master */
+    NULL,                                  /* init module */
+    NULL,                                  /* init process */
+    NULL,                                  /* init thread */
+    NULL,                                  /* exit thread */
+    NULL,                                  /* exit process */
+    NULL,                                  /* exit master */
+    NGX_MODULE_V1_PADDING
+};
+
+
+static u_char  smtp_ok[] = "235 2.0.0 OK" CRLF;
+
+
+void
+ngx_mail_proxy_init(ngx_mail_session_t *s, ngx_peer_addr_t *peer)
+{
+    int                        keepalive;
+    ngx_int_t                  rc;
+    ngx_mail_proxy_ctx_t      *p;
+    ngx_mail_proxy_conf_t     *pcf;
+    ngx_mail_core_srv_conf_t  *cscf;
+
+    s->connection->log->action = "connecting to upstream";
+
+    cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);
+
+    if (cscf->so_keepalive) {
+        keepalive = 1;
+
+        if (setsockopt(s->connection->fd, SOL_SOCKET, SO_KEEPALIVE,
+                       (const void *) &keepalive, sizeof(int))
+                == -1)
+        {
+            ngx_log_error(NGX_LOG_ALERT, s->connection->log, ngx_socket_errno,
+                          "setsockopt(SO_KEEPALIVE) failed");
+        }
+    }
+
+    p = ngx_pcalloc(s->connection->pool, sizeof(ngx_mail_proxy_ctx_t));
+    if (p == NULL) {
+        ngx_mail_session_internal_server_error(s);
+        return;
+    }
+
+    s->proxy = p;
+
+    p->upstream.sockaddr = peer->sockaddr;
+    p->upstream.socklen = peer->socklen;
+    p->upstream.name = &peer->name;
+    p->upstream.get = ngx_event_get_peer;
+    p->upstream.log = s->connection->log;
+    p->upstream.log_error = NGX_ERROR_ERR;
+
+    rc = ngx_event_connect_peer(&p->upstream);
+
+    if (rc == NGX_ERROR || rc == NGX_BUSY || rc == NGX_DECLINED) {
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    ngx_add_timer(p->upstream.connection->read, cscf->timeout);
+
+    p->upstream.connection->data = s;
+    p->upstream.connection->pool = s->connection->pool;
+
+    s->connection->read->handler = ngx_mail_proxy_block_read;
+    p->upstream.connection->write->handler = ngx_mail_proxy_dummy_handler;
+
+    pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
+
+    s->proxy->buffer = ngx_create_temp_buf(s->connection->pool,
+                                           pcf->buffer_size);
+    if (s->proxy->buffer == NULL) {
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    switch (s->protocol) {
+
+    case NGX_MAIL_POP3_PROTOCOL:
+        p->upstream.connection->read->handler = ngx_mail_proxy_pop3_handler;
+        s->mail_state = ngx_pop3_start;
+        break;
+
+    case NGX_MAIL_IMAP_PROTOCOL:
+        p->upstream.connection->read->handler = ngx_mail_proxy_imap_handler;
+        s->mail_state = ngx_imap_start;
+        break;
+
+    default: /* NGX_MAIL_SMTP_PROTOCOL */
+        p->upstream.connection->read->handler = ngx_mail_proxy_smtp_handler;
+        s->mail_state = ngx_smtp_start;
+        break;
+    }
+}
+
+
+static void
+ngx_mail_proxy_block_read(ngx_event_t *rev)
+{
+    ngx_connection_t    *c;
+    ngx_mail_session_t  *s;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy block read");
+
+    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+        c = rev->data;
+        s = c->data;
+
+        ngx_mail_proxy_close_session(s);
+    }
+}
+
+
+static void
+ngx_mail_proxy_pop3_handler(ngx_event_t *rev)
+{
+    u_char                 *p;
+    ngx_int_t               rc;
+    ngx_str_t               line;
+    ngx_connection_t       *c;
+    ngx_mail_session_t     *s;
+    ngx_mail_proxy_conf_t  *pcf;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
+                   "mail proxy pop3 auth handler");
+
+    c = rev->data;
+    s = c->data;
+
+    if (rev->timedout) {
+        ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
+                      "upstream timed out");
+        c->timedout = 1;
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    rc = ngx_mail_proxy_read_response(s, 0);
+
+    if (rc == NGX_AGAIN) {
+        return;
+    }
+
+    if (rc == NGX_ERROR) {
+        ngx_mail_proxy_upstream_error(s);
+        return;
+    }
+
+    switch (s->mail_state) {
+
+    case ngx_pop3_start:
+        ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send user");
+
+        s->connection->log->action = "sending user name to upstream";
+
+        line.len = sizeof("USER ")  - 1 + s->login.len + 2;
+        line.data = ngx_palloc(c->pool, line.len);
+        if (line.data == NULL) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
+        p = ngx_cpymem(line.data, "USER ", sizeof("USER ") - 1);
+        p = ngx_cpymem(p, s->login.data, s->login.len);
+        *p++ = CR; *p = LF;
+
+        s->mail_state = ngx_pop3_user;
+        break;
+
+    case ngx_pop3_user:
+        ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send pass");
+
+        s->connection->log->action = "sending password to upstream";
+
+        line.len = sizeof("PASS ")  - 1 + s->passwd.len + 2;
+        line.data = ngx_palloc(c->pool, line.len);
+        if (line.data == NULL) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
+        p = ngx_cpymem(line.data, "PASS ", sizeof("PASS ") - 1);
+        p = ngx_cpymem(p, s->passwd.data, s->passwd.len);
+        *p++ = CR; *p = LF;
+
+        s->mail_state = ngx_pop3_passwd;
+        break;
+
+    case ngx_pop3_passwd:
+        s->connection->read->handler = ngx_mail_proxy_handler;
+        s->connection->write->handler = ngx_mail_proxy_handler;
+        rev->handler = ngx_mail_proxy_handler;
+        c->write->handler = ngx_mail_proxy_handler;
+
+        pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
+        ngx_add_timer(s->connection->read, pcf->timeout);
+        ngx_del_timer(c->read);
+
+        c->log->action = NULL;
+        ngx_log_error(NGX_LOG_INFO, c->log, 0, "client logged in");
+
+        ngx_mail_proxy_handler(s->connection->write);
+
+        return;
+
+    default:
+#if (NGX_SUPPRESS_WARN)
+        line.len = 0;
+        line.data = NULL;
+#endif
+        break;
+    }
+
+    if (c->send(c, line.data, line.len) < (ssize_t) line.len) {
+        /*
+         * we treat the incomplete sending as NGX_ERROR
+         * because it is very strange here
+         */
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    s->proxy->buffer->pos = s->proxy->buffer->start;
+    s->proxy->buffer->last = s->proxy->buffer->start;
+}
+
+
+static void
+ngx_mail_proxy_imap_handler(ngx_event_t *rev)
+{
+    u_char                 *p;
+    ngx_int_t               rc;
+    ngx_str_t               line;
+    ngx_connection_t       *c;
+    ngx_mail_session_t     *s;
+    ngx_mail_proxy_conf_t  *pcf;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
+                   "mail proxy imap auth handler");
+
+    c = rev->data;
+    s = c->data;
+
+    if (rev->timedout) {
+        ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
+                      "upstream timed out");
+        c->timedout = 1;
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    rc = ngx_mail_proxy_read_response(s, s->mail_state);
+
+    if (rc == NGX_AGAIN) {
+        return;
+    }
+
+    if (rc == NGX_ERROR) {
+        ngx_mail_proxy_upstream_error(s);
+        return;
+    }
+
+    switch (s->mail_state) {
+
+    case ngx_imap_start:
+        ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
+                       "mail proxy send login");
+
+        s->connection->log->action = "sending LOGIN command to upstream";
+
+        line.len = s->tag.len + sizeof("LOGIN ") - 1
+                   + 1 + NGX_SIZE_T_LEN + 1 + 2;
+        line.data = ngx_palloc(c->pool, line.len);
+        if (line.data == NULL) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
+        line.len = ngx_sprintf(line.data, "%VLOGIN {%uz}" CRLF,
+                               &s->tag, s->login.len)
+                   - line.data;
+
+        s->mail_state = ngx_imap_login;
+        break;
+
+    case ngx_imap_login:
+        ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send user");
+
+        s->connection->log->action = "sending user name to upstream";
+
+        line.len = s->login.len + 1 + 1 + NGX_SIZE_T_LEN + 1 + 2;
+        line.data = ngx_palloc(c->pool, line.len);
+        if (line.data == NULL) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
+        line.len = ngx_sprintf(line.data, "%V {%uz}" CRLF,
+                               &s->login, s->passwd.len)
+                   - line.data;
+
+        s->mail_state = ngx_imap_user;
+        break;
+
+    case ngx_imap_user:
+        ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
+                       "mail proxy send passwd");
+
+        s->connection->log->action = "sending password to upstream";
+
+        line.len = s->passwd.len + 2;
+        line.data = ngx_palloc(c->pool, line.len);
+        if (line.data == NULL) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
+        p = ngx_cpymem(line.data, s->passwd.data, s->passwd.len);
+        *p++ = CR; *p = LF;
+
+        s->mail_state = ngx_imap_passwd;
+        break;
+
+    case ngx_imap_passwd:
+        s->connection->read->handler = ngx_mail_proxy_handler;
+        s->connection->write->handler = ngx_mail_proxy_handler;
+        rev->handler = ngx_mail_proxy_handler;
+        c->write->handler = ngx_mail_proxy_handler;
+
+        pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
+        ngx_add_timer(s->connection->read, pcf->timeout);
+        ngx_del_timer(c->read);
+
+        c->log->action = NULL;
+        ngx_log_error(NGX_LOG_INFO, c->log, 0, "client logged in");
+
+        ngx_mail_proxy_handler(s->connection->write);
+
+        return;
+
+    default:
+#if (NGX_SUPPRESS_WARN)
+        line.len = 0;
+        line.data = NULL;
+#endif
+        break;
+    }
+
+    if (c->send(c, line.data, line.len) < (ssize_t) line.len) {
+        /*
+         * we treat the incomplete sending as NGX_ERROR
+         * because it is very strange here
+         */
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    s->proxy->buffer->pos = s->proxy->buffer->start;
+    s->proxy->buffer->last = s->proxy->buffer->start;
+}
+
+
+static void
+ngx_mail_proxy_smtp_handler(ngx_event_t *rev)
+{
+    u_char                    *p;
+    ngx_int_t                  rc;
+    ngx_str_t                  line;
+    ngx_connection_t          *c;
+    ngx_mail_session_t        *s;
+    ngx_mail_proxy_conf_t     *pcf;
+    ngx_mail_core_srv_conf_t  *cscf;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
+                   "mail proxy smtp auth handler");
+
+    c = rev->data;
+    s = c->data;
+
+    if (rev->timedout) {
+        ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
+                      "upstream timed out");
+        c->timedout = 1;
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    rc = ngx_mail_proxy_read_response(s, s->mail_state);
+
+    if (rc == NGX_AGAIN) {
+        return;
+    }
+
+    if (rc == NGX_ERROR) {
+        ngx_mail_proxy_upstream_error(s);
+        return;
+    }
+
+    switch (s->mail_state) {
+
+    case ngx_smtp_start:
+        ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send ehlo");
+
+        s->connection->log->action = "sending HELO/EHLO to upstream";
+
+        cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);
+
+        line.len = sizeof("HELO ")  - 1 + cscf->server_name.len + 2;
+        line.data = ngx_palloc(c->pool, line.len);
+        if (line.data == NULL) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
+        pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
+
+        p = ngx_cpymem(line.data,
+                       ((s->esmtp || pcf->xclient) ? "EHLO " : "HELO "),
+                       sizeof("HELO ") - 1);
+
+        p = ngx_cpymem(p, cscf->server_name.data, cscf->server_name.len);
+        *p++ = CR; *p = LF;
+
+        s->mail_state = pcf->xclient ? ngx_smtp_helo: ngx_smtp_noxclient;
+
+        break;
+
+    case ngx_smtp_helo:
+        ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
+                       "mail proxy send xclient");
+
+        s->connection->log->action = "sending XCLIENT to upstream";
+
+        line.len = sizeof("XCLIENT PROTO=SMTP HELO= ADDR= LOGIN= "
+                          "NAME=[UNAVAILABLE]" CRLF) - 1
+                   + s->esmtp + s->smtp_helo.len
+                   + s->connection->addr_text.len + s->login.len;
+
+        line.data = ngx_palloc(c->pool, line.len);
+        if (line.data == NULL) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
+        if (s->smtp_helo.len) {
+            line.len = ngx_sprintf(line.data,
+                           "XCLIENT PROTO=%sSMTP HELO=%V ADDR=%V LOGIN=%V "
+                           "NAME=[UNAVAILABLE]" CRLF,
+                           (s->esmtp ? "E" : ""), &s->smtp_helo,
+                           &s->connection->addr_text, &s->login)
+                       - line.data;
+        } else {
+            line.len = ngx_sprintf(line.data,
+                           "XCLIENT PROTO=SMTP ADDR=%V LOGIN=%V "
+                           "NAME=[UNAVAILABLE]" CRLF,
+                           &s->connection->addr_text, &s->login)
+                       - line.data;
+        }
+
+        s->mail_state = ngx_smtp_xclient;
+        break;
+
+    case ngx_smtp_noxclient:
+    case ngx_smtp_xclient:
+
+        ngx_memcpy(s->proxy->buffer->start, smtp_ok, sizeof(smtp_ok) - 1);
+
+        s->proxy->buffer->pos = s->proxy->buffer->start;
+        s->proxy->buffer->last = s->proxy->buffer->start + sizeof(smtp_ok) - 1;
+
+        s->connection->read->handler = ngx_mail_proxy_handler;
+        s->connection->write->handler = ngx_mail_proxy_handler;
+        rev->handler = ngx_mail_proxy_handler;
+        c->write->handler = ngx_mail_proxy_handler;
+
+        pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
+        ngx_add_timer(s->connection->read, pcf->timeout);
+        ngx_del_timer(c->read);
+
+        c->log->action = NULL;
+        ngx_log_error(NGX_LOG_INFO, c->log, 0, "client logged in");
+
+        ngx_mail_proxy_handler(s->connection->write);
+
+        return;
+
+    default:
+#if (NGX_SUPPRESS_WARN)
+        line.len = 0;
+        line.data = NULL;
+#endif
+        break;
+    }
+
+    if (c->send(c, line.data, line.len) < (ssize_t) line.len) {
+        /*
+         * we treat the incomplete sending as NGX_ERROR
+         * because it is very strange here
+         */
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
+    s->proxy->buffer->pos = s->proxy->buffer->start;
+    s->proxy->buffer->last = s->proxy->buffer->start;
+}
+
+
+static void
+ngx_mail_proxy_dummy_handler(ngx_event_t *wev)
+{
+    ngx_connection_t    *c;
+    ngx_mail_session_t  *s;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_MAIL, wev->log, 0, "mail proxy dummy handler");
+
+    if (ngx_handle_write_event(wev, 0) == NGX_ERROR) {
+        c = wev->data;
+        s = c->data;
+
+        ngx_mail_proxy_close_session(s);
+    }
+}
+
+
+static ngx_int_t
+ngx_mail_proxy_read_response(ngx_mail_session_t *s, ngx_uint_t state)
+{
+    u_char                 *p;
+    ssize_t                 n;
+    ngx_buf_t              *b;
+    ngx_mail_proxy_conf_t  *pcf;
+
+    s->connection->log->action = "reading response from upstream";
+
+    b = s->proxy->buffer;
+
+    n = s->proxy->upstream.connection->recv(s->proxy->upstream.connection,
+                                            b->last, b->end - b->last);
+
+    if (n == NGX_ERROR || n == 0) {
+        return NGX_ERROR;
+    }
+
+    if (n == NGX_AGAIN) {
+        return NGX_AGAIN;
+    }
+
+    b->last += n;
+
+    if (b->last - b->pos < 5) {
+        return NGX_AGAIN;
+    }
+
+    if (*(b->last - 2) != CR || *(b->last - 1) != LF) {
+        if (b->last == b->end) {
+            *(b->last - 1) = '\0';
+            ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
+                          "upstream sent too long response line: \"%s\"",
+                          b->pos);
+            return NGX_ERROR;
+        }
+
+        return NGX_AGAIN;
+    }
+
+    p = b->pos;
+
+    switch (s->protocol) {
+
+    case NGX_MAIL_POP3_PROTOCOL:
+        if (p[0] == '+' && p[1] == 'O' && p[2] == 'K') {
+            return NGX_OK;
+        }
+        break;
+
+    case NGX_MAIL_IMAP_PROTOCOL:
+        switch (state) {
+
+        case ngx_imap_start:
+            if (p[0] == '*' && p[1] == ' ' && p[2] == 'O' && p[3] == 'K') {
+                return NGX_OK;
+            }
+            break;
+
+        case ngx_imap_login:
+        case ngx_imap_user:
+            if (p[0] == '+') {
+                return NGX_OK;
+            }
+            break;
+
+        case ngx_imap_passwd:
+            if (ngx_strncmp(p, s->tag.data, s->tag.len) == 0) {
+                p += s->tag.len;
+                if (p[0] == 'O' && p[1] == 'K') {
+                    return NGX_OK;
+                }
+            }
+            break;
+        }
+
+        break;
+
+    default: /* NGX_MAIL_SMTP_PROTOCOL */
+        switch (state) {
+
+        case ngx_smtp_helo:
+        case ngx_smtp_noxclient:
+	    if (p[0] == '2' && p[1] == '5' && p[2] == '0') {
+		return NGX_OK;
+	    }
+	    break;
+
+        case ngx_smtp_start:
+        case ngx_smtp_xclient:
+	    if (p[0] == '2' && p[1] == '2' && p[2] == '0') {
+		return NGX_OK;
+	    }
+	    break;
+        }
+
+	break;
+    }
+
+    pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
+
+    if (pcf->pass_error_message == 0) {
+        *(b->last - 2) = '\0';
+        ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
+                      "upstream sent invalid response: \"%s\"", p);
+        return NGX_ERROR;
+    }
+
+    s->out.len = b->last - p - 2;
+    s->out.data = p;
+
+    ngx_log_error(NGX_LOG_INFO, s->connection->log, 0,
+                  "upstream sent invalid response: \"%V\"", &s->out);
+
+    s->out.len = b->last - b->pos;
+    s->out.data = b->pos;
+
+    return NGX_ERROR;
+}
+
+
+static void
+ngx_mail_proxy_handler(ngx_event_t *ev)
+{
+    char                   *action, *recv_action, *send_action;
+    size_t                  size;
+    ssize_t                 n;
+    ngx_buf_t              *b;
+    ngx_uint_t              do_write;
+    ngx_connection_t       *c, *src, *dst;
+    ngx_mail_session_t     *s;
+    ngx_mail_proxy_conf_t  *pcf;
+
+    c = ev->data;
+    s = c->data;
+
+    if (ev->timedout) {
+        c->log->action = "proxying";
+
+        if (c == s->connection) {
+            ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
+                          "client timed out");
+            c->timedout = 1;
+
+        } else {
+            ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
+                          "upstream timed out");
+        }
+
+        ngx_mail_proxy_close_session(s);
+        return;
+    }
+
+    if (c == s->connection) {
+        if (ev->write) {
+            recv_action = "proxying and reading from upstream";
+            send_action = "proxying and sending to client";
+            src = s->proxy->upstream.connection;
+            dst = c;
+            b = s->proxy->buffer;
+
+        } else {
+            recv_action = "proxying and reading from client";
+            send_action = "proxying and sending to upstream";
+            src = c;
+            dst = s->proxy->upstream.connection;
+            b = s->buffer;
+        }
+
+    } else {
+        if (ev->write) {
+            recv_action = "proxying and reading from client";
+            send_action = "proxying and sending to upstream";
+            src = s->connection;
+            dst = c;
+            b = s->buffer;
+
+        } else {
+            recv_action = "proxying and reading from upstream";
+            send_action = "proxying and sending to client";
+            src = c;
+            dst = s->connection;
+            b = s->proxy->buffer;
+        }
+    }
+
+    do_write = ev->write ? 1 : 0;
+
+    ngx_log_debug3(NGX_LOG_DEBUG_MAIL, ev->log, 0,
+                   "mail proxy handler: %d, #%d > #%d",
+                   do_write, src->fd, dst->fd);
+
+    for ( ;; ) {
+
+        if (do_write) {
+
+            size = b->last - b->pos;
+
+            if (size && dst->write->ready) {
+                c->log->action = send_action;
+
+                n = dst->send(dst, b->pos, size);
+
+                if (n == NGX_ERROR) {
+                    ngx_mail_proxy_close_session(s);
+                    return;
+                }
+
+                if (n > 0) {
+                    b->pos += n;
+
+                    if (b->pos == b->last) {
+                        b->pos = b->start;
+                        b->last = b->start;
+                    }
+                }
+            }
+        }
+
+        size = b->end - b->last;
+
+        if (size && src->read->ready) {
+            c->log->action = recv_action;
+
+            n = src->recv(src, b->last, size);
+
+            if (n == NGX_AGAIN || n == 0) {
+                break;
+            }
+
+            if (n > 0) {
+                do_write = 1;
+                b->last += n;
+
+                continue;
+            }
+
+            if (n == NGX_ERROR) {
+                src->read->eof = 1;
+            }
+        }
+
+        break;
+    }
+
+    c->log->action = "proxying";
+
+    if ((s->connection->read->eof || s->proxy->upstream.connection->read->eof)
+        && s->buffer->pos == s->buffer->last
+        && s->proxy->buffer->pos == s->proxy->buffer->last)
+    {
+        action = c->log->action;
+        c->log->action = NULL;
+        ngx_log_error(NGX_LOG_INFO, c->log, 0, "proxied session done");
+        c->log->action = action;
+
+        ngx_mail_proxy_close_session(s);
+        return;
+    }
+
+    if (ngx_handle_write_event(dst->write, 0) == NGX_ERROR) {
+        ngx_mail_proxy_close_session(s);
+        return;
+    }
+
+    if (ngx_handle_read_event(dst->read, 0) == NGX_ERROR) {
+        ngx_mail_proxy_close_session(s);
+        return;
+    }
+
+    if (ngx_handle_write_event(src->write, 0) == NGX_ERROR) {
+        ngx_mail_proxy_close_session(s);
+        return;
+    }
+
+    if (ngx_handle_read_event(src->read, 0) == NGX_ERROR) {
+        ngx_mail_proxy_close_session(s);
+        return;
+    }
+
+    if (c == s->connection) {
+        pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
+        ngx_add_timer(c->read, pcf->timeout);
+    }
+}
+
+
+static void
+ngx_mail_proxy_upstream_error(ngx_mail_session_t *s)
+{
+    if (s->proxy->upstream.connection) {
+        ngx_log_debug1(NGX_LOG_DEBUG_MAIL, s->connection->log, 0,
+                       "close mail proxy connection: %d",
+                       s->proxy->upstream.connection->fd);
+
+        ngx_close_connection(s->proxy->upstream.connection);
+    }
+
+    if (s->out.len == 0) {
+        ngx_mail_session_internal_server_error(s);
+        return;
+    }
+
+    s->quit = 1;
+    ngx_mail_send(s->connection->write);
+}
+
+
+static void
+ngx_mail_proxy_internal_server_error(ngx_mail_session_t *s)
+{
+    if (s->proxy->upstream.connection) {
+        ngx_log_debug1(NGX_LOG_DEBUG_MAIL, s->connection->log, 0,
+                       "close mail proxy connection: %d",
+                       s->proxy->upstream.connection->fd);
+
+        ngx_close_connection(s->proxy->upstream.connection);
+    }
+
+    ngx_mail_session_internal_server_error(s);
+}
+
+
+static void
+ngx_mail_proxy_close_session(ngx_mail_session_t *s)
+{
+    if (s->proxy->upstream.connection) {
+        ngx_log_debug1(NGX_LOG_DEBUG_MAIL, s->connection->log, 0,
+                       "close mail proxy connection: %d",
+                       s->proxy->upstream.connection->fd);
+
+        ngx_close_connection(s->proxy->upstream.connection);
+    }
+
+    ngx_mail_close_connection(s->connection);
+}
+
+
+static void *
+ngx_mail_proxy_create_conf(ngx_conf_t *cf)
+{
+    ngx_mail_proxy_conf_t  *pcf;
+
+    pcf = ngx_pcalloc(cf->pool, sizeof(ngx_mail_proxy_conf_t));
+    if (pcf == NULL) {
+        return NGX_CONF_ERROR;
+    }
+
+    pcf->enable = NGX_CONF_UNSET;
+    pcf->pass_error_message = NGX_CONF_UNSET;
+    pcf->xclient = NGX_CONF_UNSET;
+    pcf->buffer_size = NGX_CONF_UNSET_SIZE;
+    pcf->timeout = NGX_CONF_UNSET_MSEC;
+
+    return pcf;
+}
+
+
+static char *
+ngx_mail_proxy_merge_conf(ngx_conf_t *cf, void *parent, void *child)
+{
+    ngx_mail_proxy_conf_t *prev = parent;
+    ngx_mail_proxy_conf_t *conf = child;
+
+    ngx_conf_merge_value(conf->enable, prev->enable, 0);
+    ngx_conf_merge_value(conf->pass_error_message, prev->pass_error_message, 0);
+    ngx_conf_merge_value(conf->xclient, prev->xclient, 1);
+    ngx_conf_merge_size_value(conf->buffer_size, prev->buffer_size,
+                              (size_t) ngx_pagesize);
+    ngx_conf_merge_msec_value(conf->timeout, prev->timeout, 24 * 60 * 60000);
+
+    return NGX_CONF_OK;
+}