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+Forwarding parameters in IMAP/POP3/LMTP/SMTP proxying
+=====================================================
+
+Dovecot supports proxying various pieces of information and even variables for
+various protocols when forwarding connection.It requires that the sender is
+listed under 'trusted_networks'. For IMAP, it uses the 'ID' command, for other
+protocols,'XCLIENT' is used.
+
+This feature is supported since v1.2, except for x-forward which was added in
+v2.2.29.
+
+IMAP protocol
+-------------
+
+For IMAP protocol, this is done by extending the ID command. The maximum length
+of parameters to parse is 255 bytes.The parameters are forwarded as part of the
+ID command key-value list.
+
+'5 ID (x-originating-ip "127.0.0.1" x-originating-port "143"... )'
+
+Supported parameters
+--------------------
+
+ * 'x-originating-ip' - Client IP
+ * 'x-originating-port' - Client port
+ * 'x-connected-ip' - Server IP
+ * 'x-connected-port' - Server port
+ * 'x-proxy-ttl' - TTL which is reduced by each hop, loop prevention. When TTL
+   drops to 0, the connection is dropped.
+ * 'x-session-id' / 'x-session-ext-id' - Session ID to be used.
+ * 'x-forward-<variable_name>' - Forwarded variable, see <Variables.txt>
+
+POP3 protocol
+-------------
+
+For POP3 protocol, this is done with custom 'XCLIENT' command which accepts a
+space separated list of key=value parameters.
+
+Supported parameters
+--------------------
+
+ * 'ADDR' - Client IP
+ * 'PORT' - Client port
+ * 'SESSION' - Session ID
+ * 'TTL' - TTL which is reduced by each hop, loop prevention. When TTL drops to
+   0, the connection is dropped.
+ * 'FORWARD' - Base64 encoded key=value parameter to be stored.
+
+SMTP/LMTP protocol
+------------------
+
+See http://www.postfix.org/XCLIENT_README.html
+
+ * 'ADDR' - Client IP, IPV6: prefix is needed for IPv6.
+ * 'PORT' - Client port
+ * 'SESSION' - Session ID
+ * 'HELO' - Original HELO/EHLO
+ * 'LOGIN' - Original LOGIN value
+ * 'TIMEOUT' - Original TIMEOUT
+ * 'TTL' - TTL which is reduced by each hop, loop prevention. When TTL drops to
+   0, the connection is dropped.
+ * 'PROTO' - Forwarded protocol, can be one of SMTP, ESTMP, LMTP.
+ * 'FORWARD' - Base64 encoded key=value parameter to be stored.
+
+(This file was created from the wiki on 2019-06-19 12:42)