Unsupported Characters for Microsoft Azure

Situation

A backup plan fails with the following error message: The remote server returned an error: (400) Bad Request.

Cause

The 400 Bad Request error is returned by Microsoft Azure storage and usually means that the request sent to the server was incorrect or the server could not parse it.

In this particular case, the request can be rejected due to the presence of symbols in filenames that Microsoft Azure servers cannot process. To learn about naming rules and restrictions, refer to the Naming and Referencing Shares, Directories, Files, and Metadata article at docs.microsoft.com.

Solution

Remove any unsupported symbols in filenames in your backup source. The easiest way is to rename such files.