diff --git a/app/dashboard/templates/dashboard/setting.html b/app/dashboard/templates/dashboard/setting.html
index 6be24b01..da7023ca 100644
--- a/app/dashboard/templates/dashboard/setting.html
+++ b/app/dashboard/templates/dashboard/setting.html
@@ -132,11 +132,12 @@
       </div>
     </div>
 
-    <div class="card">
+    <div id="random-alias" class="card">
       <div class="card-body">
         <div class="card-title">Random Alias</div>
-        <div class="mb-3">Change the way random aliases are generated by default.</div>
-        <form method="post" class="form-inline">
+
+        <div class="mt-3 mb-1">Change the way random aliases are generated by default.</div>
+        <form method="post" action="#random-alias" class="form-inline">
           <input type="hidden" name="form-name" value="change-alias-generator">
           <select class="form-control mr-sm-2" name="alias-generator-scheme">
             <option value="{{ AliasGeneratorEnum.word.value }}"
@@ -148,6 +149,25 @@
           </select>
           <button class="btn btn-outline-primary">Update</button>
         </form>
+
+        {% if current_user.has_custom_domain() %}
+          <div class="mt-3 mb-1">Select the domain for random aliases.</div>
+          <form method="post" action="#random-alias" class="form-inline">
+            <input type="hidden" name="form-name" value="change-random-alias-default-domain">
+            <select class="form-control mr-sm-2" name="random-alias-default-domain">
+              <option value="" {% if not current_user.default_random_alias_domain_id %} selected {% endif %}>
+                {{ FIRST_ALIAS_DOMAIN }} (SimpleLogin domain)
+              </option>
+              {% for domain in current_user.custom_domains() %}
+              <option value="{{ domain.id }}"
+                  {% if current_user.default_random_alias_domain_id == domain.id %} selected {% endif %} >
+                {{ domain.domain }} (your domain)
+              </option>
+            {% endfor %}
+            </select>
+            <button class="btn btn-outline-primary">Update</button>
+          </form>
+        {% endif %}
       </div>
     </div>
 
diff --git a/app/dashboard/views/setting.py b/app/dashboard/views/setting.py
index 8b3b6442..d1407207 100644
--- a/app/dashboard/views/setting.py
+++ b/app/dashboard/views/setting.py
@@ -10,7 +10,7 @@ from wtforms import StringField, validators
 from wtforms.fields.html5 import EmailField
 
 from app import s3, email_utils
-from app.config import URL
+from app.config import URL, FIRST_ALIAS_DOMAIN
 from app.dashboard.base import dashboard_bp
 from app.email_utils import (
     email_domain_can_be_used_as_mailbox,
@@ -159,6 +159,30 @@ def setting():
             flash("Your preference has been updated", "success")
             return redirect(url_for("dashboard.setting"))
 
+        elif request.form.get("form-name") == "change-random-alias-default-domain":
+            default_domain = request.form.get("random-alias-default-domain")
+            if default_domain:
+                default_domain_id = int(default_domain)
+                # sanity check
+                domain = CustomDomain.get(default_domain_id)
+                if (
+                    not domain
+                    or domain.user_id != current_user.id
+                    or not domain.verified
+                ):
+                    flash(
+                        "Something went wrong, sorry for the inconvenience. Please retry. ",
+                        "error",
+                    )
+                    return redirect(url_for("dashboard.setting"))
+                current_user.default_random_alias_domain_id = default_domain_id
+            else:
+                current_user.default_random_alias_domain_id = None
+
+            db.session.commit()
+            flash("Your preference has been updated", "success")
+            return redirect(url_for("dashboard.setting"))
+
         elif request.form.get("form-name") == "change-sender-format":
             sender_format = int(request.form.get("sender-format"))
             if SenderFormatEnum.has_value(sender_format):
@@ -215,6 +239,7 @@ def setting():
         pending_email=pending_email,
         AliasGeneratorEnum=AliasGeneratorEnum,
         manual_sub=manual_sub,
+        FIRST_ALIAS_DOMAIN=FIRST_ALIAS_DOMAIN,
     )
 
 
diff --git a/app/models.py b/app/models.py
index 1cfe1e59..7f8c962b 100644
--- a/app/models.py
+++ b/app/models.py
@@ -434,6 +434,12 @@ class User(db.Model, ModelMixin, UserMixin):
     def nb_directory(self):
         return Directory.query.filter_by(user_id=self.id).count()
 
+    def has_custom_domain(self):
+        return CustomDomain.filter_by(user_id=self.id, verified=True).count() > 0
+
+    def custom_domains(self):
+        return CustomDomain.filter_by(user_id=self.id, verified=True).all()
+
     def __repr__(self):
         return f"<User {self.id} {self.name} {self.email}>"