Time to time I’m getting a feedback indicating that people are struggling to make files without extensions to be served for HTTP verification. This is rarely the case on Linux platform, but for example for IIS on Windows it is rather common.
Would it be possible to make LE servers to fallback to requesting .txt challenge file if fetching the one without extension has failed for the reason other than “can’t connect”? Basically: try fetching xxx.yyy - if failed, then try xxx.yyy.txt
That would be still compatible with how it works now, but would help those having troubles with some server configurations while attempting to provide challenge files.