fix: default to strict TLS checks if not configured

If user has not set any settings manually
and provider is not configured,
default to strict TLS checks.

Bug was introduced in
<https://github.com/deltachat/deltachat-core-rust/pull/5854>
(commit 6b4532a08e)
and affects released core 1.142.4 and 1.142.5.

The problem only affects accounts configured
using these core versions with provider
not in the provider database or when using advanced settings.

deltachat-rpc-client/tests/test_something.py

@@ -3,6 +3,7 @@ import concurrent.futures
 import json
 import logging
 import os
+import socket
 import subprocess
 import time
 from unittest.mock import MagicMock
@@ -70,6 +71,18 @@ def test_configure_starttls(acfactory) -> None:
     assert account.is_configured()
 
 
+def test_configure_ip(acfactory) -> None:
+    account = acfactory.new_preconfigured_account()
+
+    domain = account.get_config("addr").rsplit("@")[-1]
+    ip_address = socket.gethostbyname(domain)
+
+    # This should fail TLS check.
+    account.set_config("mail_server", ip_address)
+    with pytest.raises(JsonRpcError):
+        account.configure()
+
+
 def test_account(acfactory) -> None:
     alice, bob = acfactory.get_online_accounts(2)