--- dovecot-2.2.33.2.original/src/lib-mail/mail-user-hash.c	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2/src/lib-mail/mail-user-hash.c	2017-10-31 16:21:20.424866755 +0000
@@ -33,9 +33,13 @@
 		tab = t_malloc(sizeof(static_tab));
 		memcpy(tab, static_tab, sizeof(static_tab));
 		tab[0].value = username;
-		tab[1].value = t_strcut(username, '@');
-		tab[2].value = strchr(username, '@');
-		if (tab[2].value != NULL) tab[2].value++;
+		tab[2].value = strrchr(username, '@');
+		if (tab[2].value != NULL) {
+			tab[1].value = t_strndup(username, tab[2].value - username);
+			tab[2].value++;
+		} else {
+			tab[1].value = username;
+		}
 
 		var_expand(str, format, tab);
 		md5_get_digest(str_data(str), str_len(str), md5);
--- dovecot-2.2.33.2.original/src/lib-mail/message-address.c	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2/src/lib-mail/message-address.c	2017-10-31 10:12:50.185866755 +0000
@@ -540,7 +540,7 @@
 	if (*delimiter_string == '\0')
 		return;
 
-	domain = strchr(address, '@');
+	domain = strrchr(address, '@');
 	p = strstr(address, delimiter_string);
 	if (p != NULL && (domain == NULL || p < domain)) {
 		/* user+detail@domain */
--- dovecot-2.2.33.2.original/src/lib-smtp/Makefile.am	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2/src/lib-smtp/Makefile.am	2017-11-01 16:05:07.393866755 +0000
@@ -2,7 +2,8 @@
 
 AM_CPPFLAGS = \
 	-I$(top_srcdir)/src/lib \
-	-I$(top_srcdir)/src/lib-dns
+	-I$(top_srcdir)/src/lib-dns \
+	-I$(top_srcdir)/src/lib/mail
 
 libsmtp_la_SOURCES = \
 	lmtp-client.c
--- dovecot-2.2.33.2.original/src/lib-smtp/lmtp-client.c	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2/src/lib-smtp/lmtp-client.c	2017-11-01 16:09:28.384866755 +0000
@@ -8,6 +8,7 @@
 #include "ostream.h"
 #include "str.h"
 #include "dns-lookup.h"
+#include "rfc822-parser.h"
 #include "lmtp-client.h"
 
 #include <ctype.h>
@@ -778,6 +779,73 @@
 	client->data_header = p_strdup(client->pool, str);
 }
 
+/* similar to (private) str_append_maybe_escape() in lib-mail */
+static void lmtp_client_rfc822_escape_address(string_t *dest_r, const char *str)
+{
+        const char *p;
+        const char *domain;
+
+        /* no strrchrnul */
+        domain = strrchr(str, '@');
+        if (domain == NULL) {
+                domain = str;
+                while (*domain != '\0')
+                        domain++;
+        }
+
+        /* see if we need to quote local part */
+        for (p=str; p < domain; p++) {
+                if (!IS_ATEXT(*p))
+                        break;
+        }
+
+        /* local part is atext */
+        if (p == domain) {
+                str_append(dest_r, str);
+                return;
+        }
+
+        /* need to quote the local part */
+        str_append_c(dest_r, '"');
+
+        /* see if we need to escape */
+        for (p=str; p < domain; p++) {
+                if (strchr("\t\"\r\n\\", *p))
+                        break;
+        }
+
+        if (p == domain) {
+                /* only quote */
+                str_append_data(dest_r, str, (size_t)(p - str));
+        } else  {
+                /* escape local-part */
+                for (p=str; p < domain; p++) {
+                        switch (*p) {
+                        case '\t':
+                                str_append(dest_r, "\\t");
+                                break;
+                        case '"':
+                                str_append(dest_r, "\\\"");
+                                break;
+                        case '\r':
+                                str_append(dest_r, "\\r");
+                                break;
+                        case '\n':
+                                str_append(dest_r, "\\n");
+                                break;
+                        case '\\':
+                                str_append(dest_r, "\\\\");
+                                break;
+                        default:
+                                str_append_c(dest_r, *p);
+                        }
+                }
+        }
+
+        str_append_c(dest_r, '"');
+        str_append(dest_r, domain);
+}
+
 static void lmtp_append_xtext(string_t *dest, const char *str)
 {
 	unsigned int i;
@@ -800,7 +868,9 @@
 	rcpt = array_get(&client->recipients, &count);
 	for (i = client->rcpt_next_send_idx; i < count; i++) {
 		str_truncate(str, 0);
-		str_printfa(str, "RCPT TO:<%s>", rcpt[i].address);
+		str_append(str, "RCPT TO:<");
+		lmtp_client_rfc822_escape_address(str, rcpt[i].address);
+		str_append_c(str, '>');
 		if (rcpt->params.dsn_orcpt != NULL) {
 			str_append(str, " ORCPT=");
 			lmtp_append_xtext(str, rcpt->params.dsn_orcpt);
--- dovecot-2.2.33.2.original/src/lmtp/commands.c	2017-10-05 18:10:44.000000000 +0100
+++ dovecot-2.2.33.2/src/lmtp/commands.c	2017-11-01 13:07:23.614866755 +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, (const char*)parser.data);
 
-	str_append(str, p);
 	return str_c(str);
 }