Invalid character in the given encoding in "npm install" nodemailer

I tried

npm install -g mongodb formidable nodemailer simplesmtp imap

After I got an error in red line: 

.....AppData.....node_modules\iconv\build\icovcxproj(40,47)> error MSB4025: The project file could not be loaded: Invalid character in the given encoding. Line 40, position 47. ... 

npm WARN optional dep failed, continuing iconv@1.2.3 ...

and after some ERR! rows.

What can I do?

(Op: Windows 8 )

It seems that the problem is with installing one of the dependencies, iconv.

You should show us the output of npm install -g iconv. And if you can, post it to the project's issue list.

I'm not sure which of the projects (mongodb formidable nodemailer simplesmtp imap) has iconv as a dependency, but installing them separately should let you know.

npm install -g mongodb
npm install -g formidable
npm install -g nodemailer
...