fix: SMTP envelope recipients split on commas inside display names (#1464)

tests/test_email_envelope_recipients.py

@@ -0,0 +1,26 @@
+"""Regression: SMTP envelope recipients must be parsed, not split on bare commas.
+
+The send paths built the RCPT TO list with `field.split(",")`, which corrupts a
+display name containing a comma (e.g. `"Smith, John" <john@corp.com>`, the common
+Outlook / corporate address-book form): it splits into `"Smith` and
+`John" <john@corp.com>`, so the broken fragments are handed to smtp.sendmail and
+delivery fails. `_envelope_recipients` uses email.utils.getaddresses instead.
+"""
+import routes.email_routes as email_routes
+
+
+def test_display_name_with_comma_yields_one_address():
+    assert email_routes._envelope_recipients('"Smith, John" <john@corp.com>') == ["john@corp.com"]
+
+
+def test_multiple_plain_addresses():
+    assert email_routes._envelope_recipients("a@x.com, b@y.com") == ["a@x.com", "b@y.com"]
+
+
+def test_to_cc_bcc_combined_and_none_safe():
+    got = email_routes._envelope_recipients('"Doe, Jane" <jane@x.com>, bob@y.com', None, "carol@z.com")
+    assert got == ["jane@x.com", "bob@y.com", "carol@z.com"]
+
+
+def test_empty_and_none_fields():
+    assert email_routes._envelope_recipients("", None) == []