The target email text area will put wrong characters into the system IF you have rich text editors enabled. I have tinyMCE enabled by default, and even if you disable it when you are editing your signIt page, it will still put in extra characters and therefore your emails will fail.

I fixed it by changing the target email field in the code to a textfield instead of a text area. This usually means that your rich text editors will ignore this field, and this neatly circumvents any issues.