diff --git a/src/lib-lda/mail-deliver.c b/src/lib-lda/mail-deliver.c
index b7aa4ee883..ce5f2b5ab6 100644
--- a/src/lib-lda/mail-deliver.c
+++ b/src/lib-lda/mail-deliver.c
@@ -86,11 +86,13 @@ const struct smtp_address *
 mail_deliver_get_address(struct mail *mail, const char *header)
 {
 	struct message_address *addr;
+	struct smtp_address *smtp_addr;
 
 	addr = mail_deliver_get_message_address(mail, header);
-	if (addr == NULL)
+	if (addr == NULL ||
+	    smtp_address_create_from_msg_temp(addr, &smtp_addr) < 0)
 		return NULL;
-	return smtp_address_create_from_msg_temp(addr);
+	return smtp_addr;
 }
 
 static void update_cache(pool_t pool, const char **old_str, const char *new_str)
@@ -421,6 +423,7 @@ const struct smtp_address *
 mail_deliver_get_return_address(struct mail_deliver_context *ctx)
 {
 	struct message_address *addr;
+	struct smtp_address *smtp_addr;
 	const char *path;
 	int ret;
 
@@ -438,12 +441,12 @@ mail_deliver_get_return_address(struct mail_deliver_context *ctx)
 	}
 	if (message_address_parse_path(pool_datastack_create(),
 				       (const unsigned char *)path,
-				       strlen(path), &addr) < 0) {
+				       strlen(path), &addr) < 0 ||
+	    smtp_address_create_from_msg(ctx->pool, addr, &smtp_addr) < 0) {
 		i_warning("Failed to parse return-path header");
 		return NULL;
 	}
-
-	return smtp_address_create_from_msg(ctx->pool, addr);
+	return smtp_addr;
 }
 
 const char *mail_deliver_get_new_message_id(struct mail_deliver_context *ctx)
diff --git a/src/lib-smtp/smtp-address.c b/src/lib-smtp/smtp-address.c
index 9969c36a97..72e5c08bfb 100644
--- a/src/lib-smtp/smtp-address.c
+++ b/src/lib-smtp/smtp-address.c
@@ -591,12 +591,26 @@ void smtp_address_init(struct smtp_address *address,
 	address->domain = (localpart == NULL ? NULL : domain);
 }
 
-void smtp_address_init_from_msg(struct smtp_address *address,
-	const struct message_address *msg_addr)
+int smtp_address_init_from_msg(struct smtp_address *address,
+			       const struct message_address *msg_addr)
 {
+	const char *p;
+
 	i_zero(address);
+	if (msg_addr->mailbox == NULL)
+		return 0;
+
+	/* The message_address_parse() function allows UTF-8 codepoints in
+	   the localpart. For SMTP addresses that is not an option, so we
+	   need to check this upon conversion. */
+	for (p = msg_addr->mailbox; *p != '\0'; p++) {
+		if (!smtp_char_is_qpair(*p))
+			return -1;
+	}
+
 	address->localpart = msg_addr->mailbox;
-	address->domain = (msg_addr->mailbox == NULL ? NULL : msg_addr->domain);
+	address->domain = msg_addr->domain;
+	return 0;
 }
 
 struct smtp_address *
@@ -643,14 +657,19 @@ smtp_address_create(pool_t pool,
 	return smtp_address_clone(pool, &addr);
 }
 
-struct smtp_address *
-smtp_address_create_from_msg(pool_t pool,
-	const struct message_address *msg_addr)
+
+int smtp_address_create_from_msg(pool_t pool,
+				 const struct message_address *msg_addr,
+				 struct smtp_address **address_r)
 {
 	struct smtp_address addr;
 
-	smtp_address_init_from_msg(&addr, msg_addr);
-	return smtp_address_clone(pool, &addr);
+	if (smtp_address_init_from_msg(&addr, msg_addr) < 0) {
+		*address_r = NULL;
+		return -1;
+	}
+	*address_r = smtp_address_clone(pool, &addr);
+	return 0;
 }
 
 struct smtp_address *
@@ -676,13 +695,17 @@ smtp_address_create_temp(const char *localpart, const char *domain)
 	return smtp_address_clone_temp(&addr);
 }
 
-struct smtp_address *
-smtp_address_create_from_msg_temp(const struct message_address *msg_addr)
+int  smtp_address_create_from_msg_temp(const struct message_address *msg_addr,
+				       struct smtp_address **address_r)
 {
 	struct smtp_address addr;
 
-	smtp_address_init_from_msg(&addr, msg_addr);
-	return smtp_address_clone_temp(&addr);
+	if (smtp_address_init_from_msg(&addr, msg_addr) < 0) {
+		*address_r = NULL;
+		return -1;
+	}
+	*address_r = smtp_address_clone_temp(&addr);
+	return 0;
 }
 
 struct smtp_address *
diff --git a/src/lib-smtp/smtp-address.h b/src/lib-smtp/smtp-address.h
index a822b981d9..2556e4feab 100644
--- a/src/lib-smtp/smtp-address.h
+++ b/src/lib-smtp/smtp-address.h
@@ -79,8 +79,8 @@ smtp_address_encode_path(const struct smtp_address *address)
 
 void smtp_address_init(struct smtp_address *address,
 	const char *localpart, const char *domain) ATTR_NULL(2,3);
-void smtp_address_init_from_msg(struct smtp_address *address,
-	const struct message_address *msg_addr);
+int smtp_address_init_from_msg(struct smtp_address *address,
+			       const struct message_address *msg_addr);
 
 struct smtp_address *
 smtp_address_clone(pool_t pool, const struct smtp_address *address)
@@ -88,9 +88,9 @@ smtp_address_clone(pool_t pool, const struct smtp_address *address)
 struct smtp_address *
 smtp_address_create(pool_t pool, const char *localpart, const char *domain)
 	ATTR_NULL(2, 3);
-struct smtp_address *
-smtp_address_create_from_msg(pool_t pool,
-	const struct message_address *msg_addr);
+int smtp_address_create_from_msg(pool_t pool,
+				 const struct message_address *msg_addr,
+				 struct smtp_address **address_r);
 
 struct smtp_address *
 smtp_address_clone_temp(const struct smtp_address *address)
@@ -98,8 +98,8 @@ smtp_address_clone_temp(const struct smtp_address *address)
 struct smtp_address *
 smtp_address_create_temp(const char *localpart, const char *domain)
 	ATTR_NULL(2, 3);
-struct smtp_address *
-smtp_address_create_from_msg_temp(const struct message_address *msg_addr);
+int smtp_address_create_from_msg_temp(const struct message_address *msg_addr,
+				      struct smtp_address **address_r);
 
 struct smtp_address *
 smtp_address_add_detail(pool_t pool, const struct smtp_address *address,
diff --git a/src/lib-smtp/smtp-params.c b/src/lib-smtp/smtp-params.c
index d677aa5e01..ac8aa66ef3 100644
--- a/src/lib-smtp/smtp-params.c
+++ b/src/lib-smtp/smtp-params.c
@@ -705,13 +705,15 @@ smtp_params_rcpt_parse_orcpt_rfc822(const char *addr_str,
 	pool_t pool, const struct smtp_address **addr_r)
 {
 	struct message_address *rfc822_addr;
+	struct smtp_address *addr;
 
 	rfc822_addr = message_address_parse(pool_datastack_create(),
 		(const unsigned char *)addr_str, strlen(addr_str), 2, FALSE);
 	if (rfc822_addr == NULL || rfc822_addr->invalid_syntax ||
-		rfc822_addr->next != NULL)
+	    rfc822_addr->next != NULL ||
+	    smtp_address_create_from_msg(pool, rfc822_addr, &addr) < 0)
 		return -1;
-	*addr_r = smtp_address_create_from_msg(pool, rfc822_addr);
+	*addr_r = addr;
 	return 0;
 }