> How to handle similar breakage of external servers?

For tests with the external environment,
How about skipping tests if servers are not available?
It is assumed that if there is a change related to NNTP, it is well checked in the CI and review.
This is because, at this point, reviewers and patch submitters check whether tests with external servers are passed.

The reason for testing with the outside is to confirm that the whole operation works well.
If external servers are not available, we can emit warning messages so that we can recognize when an issue occurs.

Other than that, I can think of local server testing or mocking testing, but I am not sure if it is easy way for the SSL environment.