Attachments empty

Linode has made a security upgrade on my server and now it is not possible to attach files to an e-mail.

It shows the attachment in the right side, but when clicking/opening I got an error message:

Warning:,Expected: application/pdf (.pdf); Found: application/x-empty
No other errors, but the send e-mail has no attachments.

Can it be a missing tmp dir. or a permission problem?

Any help appreciated.

Look at nginx error.log file, it will tell you what happens when you upload the file.