diff --git a/app/email_utils.py b/app/email_utils.py
index eb466794..912bfd3e 100644
--- a/app/email_utils.py
+++ b/app/email_utils.py
@@ -39,7 +39,7 @@ from app.dns_utils import get_mx_domains
 from app.extensions import db
 from app.log import LOG
 from app.models import Mailbox, User, SentAlert, CustomDomain, SLDomain, Contact
-from app.utils import random_string
+from app.utils import random_string, convert_to_id
 
 
 def render(template_name, **kwargs) -> str:
@@ -739,6 +739,11 @@ def generate_reply_email(contact_email: str) -> str:
         # control char: 4 chars (ra+, +)
         # random suffix: max 10 chars
         # maximum: 64
+
+        # make sure contact_email can be ascii-encoded
+        contact_email = convert_to_id(contact_email)
+        # remove potential space
+        contact_email = contact_email.replace(" ", "")
         contact_email = contact_email[:45]
         contact_email = contact_email.replace("@", ".at.")
 
diff --git a/tests/test_email_utils.py b/tests/test_email_utils.py
index ab1cbca3..8baa6d09 100644
--- a/tests/test_email_utils.py
+++ b/tests/test_email_utils.py
@@ -403,6 +403,9 @@ def test_generate_reply_email(flask_client):
     assert reply_email.startswith("ra+")
     assert reply_email.endswith(EMAIL_DOMAIN)
 
+    reply_email = generate_reply_email("👌汉字@example.org")
+    assert reply_email.startswith("ra+YiZi.at.example.org+")
+
 
 def test_get_addrs_from_header():
     msg = email.message_from_string("""To: abcd@test.org""")