use email_validator and isascii

Author: harminius

server/mergin/auth/forms.py

@@ -17,6 +17,7 @@
 
 from .models import MAX_USERNAME_LENGTH, User
 from ..app import UpdateForm, CustomStringField
+from .utils import get_email_domain
 
 
 def username_validation(form, field):
@@ -64,13 +65,8 @@ def __call__(self, form, field):
                 f"Email address '{field.data}' contains an invalid character."
             )
 
-        try:
-            local_part, domain_part = field.data.rsplit("@", 1)
-        except ValueError:
-            raise ValidationError(f"Invalid email address '{field.data}'.")
-
-        # character is one of the standard ASCII characters (0–127)
-        if not all(ord(c) < 128 for c in domain_part):
+        domain = get_email_domain(field.data)
+        if not domain.isascii():
             raise ValidationError(
                 f"Email address '{field.data}' contains non-ASCII characters in the domain part."
             )

server/mergin/auth/utils.py

@@ -0,0 +1,13 @@
+# Copyright (C) Lutra Consulting Limited
+#
+# SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-MerginMaps-Commercial
+
+from email_validator import validate_email, EmailNotValidError
+
+
+def get_email_domain(email: str) -> str | None:
+    try:
+        result = validate_email(email, check_deliverability=False)
+        return result.domain
+    except EmailNotValidError:
+        return