diff --git a/app/config.py b/app/config.py
index a1224ec0..ef505d2b 100644
--- a/app/config.py
+++ b/app/config.py
@@ -79,6 +79,9 @@ else:
 # List of domains user can use to create alias
 ALIAS_DOMAINS = OTHER_ALIAS_DOMAINS + [EMAIL_DOMAIN]
 
+# the alias domain used when creating the first alias for user
+FIRST_ALIAS_DOMAIN = os.environ.get("FIRST_ALIAS_DOMAIN") or EMAIL_DOMAIN
+
 # list of (priority, email server)
 EMAIL_SERVERS_WITH_PRIORITY = eval(
     os.environ["EMAIL_SERVERS_WITH_PRIORITY"]
diff --git a/example.env b/example.env
index a9b29f9e..a2747523 100644
--- a/example.env
+++ b/example.env
@@ -21,6 +21,9 @@ EMAIL_DOMAIN=sl.local
 # other domains that can be used to create aliases, in addition to EMAIL_DOMAIN
 OTHER_ALIAS_DOMAINS=["domain1.com", "domain2.com"]
 
+# the alias domain used when creating the first alias for user, default to EMAIL_DOMAIN if not set
+# FIRST_ALIAS_DOMAIN = another-domain.com
+
 # transactional email is sent from this email address
 SUPPORT_EMAIL=support@sl.local
 SUPPORT_NAME=Son from SimpleLogin