<inp2:m_AttachFile path="..."/> tag is designed to be called from within e-mail template to be able to attach any file to e-mail, which is being sent right now.
Tag works fine in following cases:
- the "path" argument value is not empty and file exists - file is attached
- the "path" argument value is not empty and file doesn't exist - file isn't attached
The case however, that isn't covered is when "path" argument value is empty. In that case it's prepended with DocumentRoot, which is directory, that always exists and attempt is made to attach a directory. That in turn is blocked by e-mail sending code with following error message:
When checking if given file exists also confirm, that it's a file and not a directory.