I just tried this plugin on my development page and ran into some issues. 

1.) Parsererror

Whenever I want to send a message now, I get the alert saying "parsererror". I cannot send any private messages anymore. 

Before this error occured, I created a new account and used a link in the first message to test the anti-spam. It was flagged correct, but now I cannot send any messages with any account (admin and normal accounts) anymore and only get parsererror messages. 

Idea: Could this be linked to the fact that I am testing this plugin with the same IP adress? So all messaging from this IP adress is now locked, no matter with account I use?

2.) Message "undefined"

To test the system, I created a new account and send a message with a link. It was not working as intended, but I only got an "undefined" error message to see. 

Can you show me where to translate this message? I have not found the string in the language file. 

Thank you

Matthias