new file mode 100644
--- /dev/null
+++ b/src/imap/ngx_imap.h
@@ -0,0 +1,189 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#ifndef _NGX_IMAP_H_INCLUDED_
+#define _NGX_IMAP_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+#include <ngx_event_connect.h>
+
+
+typedef struct {
+    void   **main_conf;
+    void   **srv_conf;
+} ngx_imap_conf_ctx_t;
+
+
+typedef struct {
+    ngx_array_t           servers;         /* ngx_imap_core_srv_conf_t */
+} ngx_imap_core_main_conf_t;
+
+
+#define NGX_IMAP_POP3_PROTOCOL  0
+#define NGX_IMAP_IMAP_PROTOCOL  1
+
+typedef struct {
+    ngx_msec_t            timeout;
+
+    size_t                imap_client_buffer_size;
+    size_t                proxy_buffer_size;
+
+    ngx_uint_t            protocol;
+
+    ngx_buf_t            *pop3_capability;
+    ngx_buf_t            *imap_capability;
+
+    ngx_array_t           pop3_capabilities;
+    ngx_array_t           imap_capabilities;
+
+    /* server ctx */
+    ngx_imap_conf_ctx_t  *ctx;
+} ngx_imap_core_srv_conf_t;
+
+
+typedef struct {
+    void       *(*create_main_conf)(ngx_conf_t *cf);
+    char       *(*init_main_conf)(ngx_conf_t *cf, void *conf);
+
+    void       *(*create_srv_conf)(ngx_conf_t *cf);
+    char       *(*merge_srv_conf)(ngx_conf_t *cf, void *prev, void *conf);
+} ngx_imap_module_t;
+
+
+typedef enum {
+    ngx_imap_start = 0,
+    ngx_imap_login,
+    ngx_imap_user,
+    ngx_imap_passwd,
+} ngx_imap_state_e;
+
+
+typedef enum {
+    ngx_pop3_start = 0,
+    ngx_pop3_user,
+    ngx_pop3_passwd
+} ngx_po3_state_e;
+
+
+typedef struct {
+    ngx_peer_connection_t   upstream;
+    ngx_buf_t              *buffer;
+} ngx_imap_proxy_ctx_t;
+
+
+typedef struct {
+    uint32_t                signature;         /* "IMAP" */
+
+    ngx_connection_t       *connection;
+
+    ngx_buf_t              *buffer;
+    ngx_str_t               out;
+
+    void                  **ctx;
+    void                  **main_conf;
+    void                  **srv_conf;
+
+    ngx_imap_proxy_ctx_t   *proxy;
+
+    ngx_uint_t              imap_state;
+
+    unsigned                protocol:1;
+    unsigned                quoted:1;
+
+    ngx_str_t               login;
+    ngx_str_t               passwd;
+
+    ngx_str_t               tag;
+
+    ngx_uint_t              command;
+    ngx_array_t             args;
+
+    ngx_uint_t              login_attempt;
+
+    /* used to parse IMAP/POP3 command */
+
+    ngx_uint_t              state;
+    u_char                 *cmd_start;
+    u_char                 *arg_start;
+    u_char                 *arg_end;
+    ngx_uint_t              literal_len;
+} ngx_imap_session_t;
+
+
+#define NGX_POP3_USER       1
+#define NGX_POP3_PASS       2
+#define NGX_POP3_CAPA       3
+#define NGX_POP3_QUIT       4
+#define NGX_POP3_NOOP       5
+#define NGX_POP3_APOP       6
+#define NGX_POP3_STAT       7
+#define NGX_POP3_LIST       8
+#define NGX_POP3_RETR       9
+#define NGX_POP3_DELE       10
+#define NGX_POP3_RSET       11
+#define NGX_POP3_TOP        12
+#define NGX_POP3_UIDL       13
+
+
+#define NGX_IMAP_LOGIN      1
+#define NGX_IMAP_LOGOUT     2
+#define NGX_IMAP_CAPABILITY 3
+#define NGX_IMAP_NOOP       4
+
+#define NGX_IMAP_NEXT       5
+
+
+#define NGX_IMAP_PARSE_INVALID_COMMAND  20
+
+
+#define NGX_IMAP_PROXY_INVALID  10
+#define NGX_IMAP_PROXY_ERROR    11
+
+
+#define NGX_IMAP_MODULE      0x50414D49     /* "IMAP" */
+
+#define NGX_IMAP_MAIN_CONF   0x02000000
+#define NGX_IMAP_SRV_CONF    0x04000000
+
+
+#define NGX_IMAP_MAIN_CONF_OFFSET  offsetof(ngx_imap_conf_ctx_t, main_conf)
+#define NGX_IMAP_SRV_CONF_OFFSET   offsetof(ngx_imap_conf_ctx_t, srv_conf)
+
+
+#define ngx_imap_get_module_ctx(s, module)     (s)->ctx[module.ctx_index]
+#define ngx_imap_set_ctx(s, c, module)         s->ctx[module.ctx_index] = c;
+#define ngx_imap_delete_ctx(s, module)         s->ctx[module.ctx_index] = NULL;
+
+
+#define ngx_imap_get_module_main_conf(s, module)                             \
+    (s)->main_conf[module.ctx_index]
+#define ngx_imap_get_module_srv_conf(s, module)  (s)->srv_conf[module.ctx_index]
+
+
+void ngx_imap_init_connection(ngx_connection_t *c);
+void ngx_imap_auth_state(ngx_event_t *rev);
+void ngx_pop3_auth_state(ngx_event_t *rev);
+void ngx_imap_close_connection(ngx_connection_t *c);
+void ngx_imap_session_internal_server_error(ngx_imap_session_t *s);
+
+ngx_int_t ngx_imap_parse_command(ngx_imap_session_t *s);
+ngx_int_t ngx_pop3_parse_command(ngx_imap_session_t *s);
+
+
+/* STUB */
+void ngx_imap_proxy_init(ngx_imap_session_t *s, ngx_peers_t *peers);
+void ngx_imap_auth_http_init(ngx_imap_session_t *s);
+/**/
+
+
+extern ngx_uint_t    ngx_imap_max_module;
+extern ngx_module_t  ngx_imap_core_module;
+
+
+#endif /* _NGX_IMAP_H_INCLUDED_ */