--- dovecot-2.2.33.2/src/lib-mail/message-address.c	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2.quoted-local-proxy/src/lib-mail/message-address.c	2017-11-02 12:21:57.572866755 +0000
@@ -34,7 +34,7 @@
 }
 
 /* quote with "" and escape all '\', '"' and "'" characters if need */
-static void str_append_maybe_escape(string_t *dest, const char *cstr, bool escape_dot)
+void str_append_maybe_escape(string_t *dest, const char *cstr, bool escape_dot)
 {
 	const char *p;
 
--- dovecot-2.2.33.2/src/lib-mail/message-address.h	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2.quoted-local-proxy/src/lib-mail/message-address.h	2017-11-02 13:22:45.093866755 +0000
@@ -39,4 +39,7 @@
 				  const char *address, const char **username_r,
 				  const char **detail_r);
 
+/* quote with "" and escape all '\', '"' and "'" characters if need */
+void str_append_maybe_escape(string_t *dest, const char *cstr, bool escape_dot);
+
 #endif
--- dovecot-2.2.33.2/src/lmtp/commands.c	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2.quoted-local-proxy/src/lmtp/commands.c	2017-11-02 13:50:25.794866755 +0000
@@ -441,34 +441,18 @@
 
 static const char *lmtp_unescape_address(const char *name)
 {
+	struct rfc822_parser_context parser;
 	string_t *str;
-	const char *p;
 
 	if (*name != '"')
 		return name;
 
-	/* quoted-string local-part. drop the quotes unless there's a
-	   '@' character inside or there's an error. */
+	/* decode quoted-string local-part */
 	str = t_str_new(128);
-	for (p = name+1; *p != '"'; p++) {
-		if (*p == '\0')
-			return name;
-		if (*p == '\\') {
-			if (p[1] == '\0') {
-				/* error */
-				return name;
-			}
-			p++;
-		}
-		if (*p == '@')
-			return name;
-		str_append_c(str, *p);
-	}
-	p++;
-	if (*p != '@' && *p != '\0')
-		return name;
+	rfc822_parser_init(&parser, (const unsigned char*)name, strlen(name), NULL);
+	rfc822_parse_quoted_string(&parser, str);
 
-	str_append(str, p);
+	str_append(str, (const char*)parser.data);
 	return str_c(str);
 }
 
--- dovecot-2.2.33.2/src/lmtp/lmtp-proxy.c	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2.quoted-local-proxy/src/lmtp/lmtp-proxy.c	2017-11-02 13:49:41.154866755 +0000
@@ -8,6 +8,7 @@
 #include "ostream.h"
 #include "str.h"
 #include "time-util.h"
+#include "message-address.h"
 #include "lmtp-client.h"
 #include "lmtp-proxy.h"
 
@@ -288,6 +289,24 @@
 	lmtp_proxy_try_finish(conn->proxy);
 }
 
+static char *lmtp_proxy_escape_address(pool_t pool, const char *address) {
+	const char *domain;
+	string_t *dest;
+
+	domain = strrchr(address, '@');
+	dest = str_new(pool, 128);
+
+	if (domain == NULL) {
+		str_append_maybe_escape(dest, address, FALSE);
+	} else {
+		const char *local_part = t_strdup_until(address, domain);
+		str_append_maybe_escape(dest, local_part, FALSE);
+		str_append(dest, domain);
+	}
+
+	return str_free_without_data(&dest);
+}
+
 int lmtp_proxy_add_rcpt(struct lmtp_proxy *proxy, const char *address,
 			const struct lmtp_proxy_rcpt_settings *set)
 {
@@ -301,10 +320,10 @@
 	rcpt = p_new(proxy->pool, struct lmtp_proxy_recipient, 1);
 	rcpt->idx = array_count(&proxy->rcpt_to);
 	rcpt->conn = conn;
-	rcpt->address = p_strdup(proxy->pool, address);
+	rcpt->address = lmtp_proxy_escape_address(proxy->pool, address);
 	array_append(&proxy->rcpt_to, &rcpt, 1);
 
-	lmtp_client_add_rcpt_params(conn->client, address, &set->params,
+	lmtp_client_add_rcpt_params(conn->client, rcpt->address, &set->params,
 				    lmtp_proxy_conn_rcpt_to,
 				    lmtp_proxy_conn_data, rcpt);
 	return 0;