diff --git a/modoboa/admin/handlers.py b/modoboa/admin/handlers.py
index e297fd3b4..35ed3ee9b 100644
--- a/modoboa/admin/handlers.py
+++ b/modoboa/admin/handlers.py
@@ -193,7 +193,7 @@ def import_account_mailbox(sender, user, account, row, **kwargs):
     :param User account: account being imported
     :param list rom: list of fields (strings)
     """
-    account.email = row[0].strip()
+    account.email = row[0].strip().lower()
     if account.email:
         mailbox, domname = split_mailbox(account.email)
         domain = models.Domain.objects.filter(name=domname).first()
diff --git a/modoboa/admin/tests/test_import_.py b/modoboa/admin/tests/test_import_.py
index 73d8aea76..d468144f6 100644
--- a/modoboa/admin/tests/test_import_.py
+++ b/modoboa/admin/tests/test_import_.py
@@ -89,7 +89,7 @@ domainalias;test.alias;test.com;True
 
         f = ContentFile(b"""
 account; user1@test.com; toto; User; One; True; SimpleUsers; user1@test.com; 0
-account; truc@test.com; toto; René; Truc; True; DomainAdmins; truc@test.com; 5; test.com
+account; Truc@test.com; toto; René; Truc; True; DomainAdmins; truc@test.com; 5; test.com
 alias; alias1@test.com; True; user1@test.com
 forward; alias2@test.com; True; user1+ext@test.com
 forward; fwd1@test.com; True; user@extdomain.com
diff --git a/modoboa/core/models.py b/modoboa/core/models.py
index 7d815c1c8..c6f89ae19 100644
--- a/modoboa/core/models.py
+++ b/modoboa/core/models.py
@@ -366,7 +366,7 @@ class User(PermissionsMixin):
                     "yours"
                 ))
 
-        self.username = row[1].strip()
+        self.username = row[1].strip().lower()
         try:
             User.objects.get(username=self.username)
         except User.DoesNotExist: