diff --git a/app/email_utils.py b/app/email_utils.py
index 6b43dd72..69a94654 100644
--- a/app/email_utils.py
+++ b/app/email_utils.py
@@ -1078,7 +1078,9 @@ def generate_reply_email(contact_email: str, user: User) -> str:
         contact_email = convert_to_id(contact_email)
         contact_email = sanitize_email(contact_email)
         contact_email = contact_email[:45]
-        contact_email = contact_email.replace("@", ".at.")
+        # use _ instead of . to avoid AC_FROM_MANY_DOTS SpamAssassin rule
+        contact_email = contact_email.replace("@", "_at_")
+        contact_email = contact_email.replace(".", "_")
         contact_email = convert_to_alphanumeric(contact_email)
 
     # not use while to avoid infinite loop
diff --git a/tests/test_email_utils.py b/tests/test_email_utils.py
index 94b57e0b..b6a4f2f8 100644
--- a/tests/test_email_utils.py
+++ b/tests/test_email_utils.py
@@ -500,18 +500,18 @@ def test_generate_reply_email_include_sender_in_reverse_alias(flask_client):
     user.include_sender_in_reverse_alias = True
 
     reply_email = generate_reply_email("test@example.org", user)
-    assert reply_email.startswith("test.at.example.org")
+    assert reply_email.startswith("test_at_example_org")
     assert reply_email.endswith(EMAIL_DOMAIN)
 
     reply_email = generate_reply_email("", user)
     assert reply_email.endswith(EMAIL_DOMAIN)
 
     reply_email = generate_reply_email("👌汉字@example.org", user)
-    assert reply_email.startswith("yizi.at.example.org")
+    assert reply_email.startswith("yizi_at_example_org")
 
     # make sure reply_email only contain lowercase
     reply_email = generate_reply_email("TEST@example.org", user)
-    assert reply_email.startswith("test.at.example.org")
+    assert reply_email.startswith("test_at_example_org")
 
 
 def test_normalize_reply_email(flask_client):