diff --git a/core/admin/mailu/internal/views/postfix.py b/core/admin/mailu/internal/views/postfix.py
index 3482b290..f8346bb1 100644
--- a/core/admin/mailu/internal/views/postfix.py
+++ b/core/admin/mailu/internal/views/postfix.py
@@ -33,8 +33,9 @@ def postfix_alias_map(alias):
     localpart, domain_name = models.Email.resolve_domain(alias)
     if localpart is None:
         return flask.jsonify(domain_name)
-    destination = models.Email.resolve_destination(localpart, domain_name)
-    return flask.jsonify(",".join(destination)) if destination else flask.abort(404)
+    if destinations := models.Email.resolve_destination(localpart, domain_name):
+        return flask.jsonify(",".join(idna_encode(destinations)))
+    return flask.abort(404)
 
 @internal.route("/postfix/transport/<path:email>")
 def postfix_transport(email):
@@ -142,9 +143,11 @@ def postfix_sender_login(sender):
     if localpart is None:
         return flask.jsonify(",".join(wildcard_senders)) if wildcard_senders else flask.abort(404)
     localpart = localpart[:next((i for i, ch in enumerate(localpart) if ch in flask.current_app.config.get('RECIPIENT_DELIMITER')), None)]
-    destination = models.Email.resolve_destination(localpart, domain_name, True)
-    destination = [*destination, *wildcard_senders] if destination else [*wildcard_senders]
-    return flask.jsonify(",".join(destination)) if destination else flask.abort(404)
+    destinations = models.Email.resolve_destination(localpart, domain_name, True) or []
+    destinations.extend(wildcard_senders)
+    if destinations:
+        return flask.jsonify(",".join(idna_encode(destinations)))
+    return flask.abort(404)
 
 @internal.route("/postfix/sender/rate/<path:sender>")
 def postfix_sender_rate(sender):
@@ -169,3 +172,11 @@ def postfix_sender_access(sender):
         except sqlalchemy.exc.StatementError:
             pass
     return flask.abort(404)
+
+# idna encode domain part of each address in list of addresses
+def idna_encode(addresses):
+    return [
+        f"{localpart}@{idna.encode(domain).decode('ascii')}"
+        for (localpart, domain) in
+        (address.rsplit("@", 1) for address in addresses)
+    ]