diff --git a/app/api/views/new_custom_alias.py b/app/api/views/new_custom_alias.py
index b6f77c11..e4c66ebe 100644
--- a/app/api/views/new_custom_alias.py
+++ b/app/api/views/new_custom_alias.py
@@ -3,11 +3,11 @@ from flask import jsonify, request
 from flask_cors import cross_origin
 
 from app.api.base import api_bp, verify_api_key
-from app.config import MAX_NB_EMAIL_FREE_PLAN
+from app.config import MAX_NB_EMAIL_FREE_PLAN, ALIAS_DOMAINS
 from app.dashboard.views.custom_alias import verify_prefix_suffix
 from app.extensions import db
 from app.log import LOG
-from app.models import GenEmail, AliasUsedOn, User
+from app.models import GenEmail, AliasUsedOn, User, CustomDomain
 from app.utils import convert_to_id
 
 
@@ -61,6 +61,14 @@ def new_custom_alias():
     gen_email = GenEmail.create(
         user_id=user.id, email=full_alias, mailbox_id=user.default_mailbox_id, note=note
     )
+
+    if alias_suffix.startswith("@"):
+        alias_domain = alias_suffix[1:]
+        if alias_domain not in ALIAS_DOMAINS:
+            domain = CustomDomain.get_by(domain=alias_domain)
+            LOG.d("set alias %s to domain %s", full_alias, domain)
+            gen_email.custom_domain_id = domain.id
+
     db.session.commit()
 
     if hostname: