Pathnames for files on the server can have up to 255 characters, including the server name, volume name, path delimiters, filename, and file extension. If a user maps a drive letter to a location deep down the directory path, and subsequently creates a pathname that exceeds the limit for the name on the server, the file cannot be saved. Even if the file’s path does not exceed 255 characters with respect to the mapped drive letter, it exceeds the maximum length on the server.
When mapping a drive letter to a folder deep down the directory path, users should adopt conventions for naming files and directories and for creating directory structures so that they do not exceed the 255-character pathname limit on the server.