Do you have a link to your site so we can have a look? I could be wrong but I dont recall that errormessage from the Php-Fusion system. Maybe this error is related to your host; I'm not sure.
It's safer if you contact me (someone else could say they are me, and you would send password to wrong person). You find my emailadress, etc. in my profile (here)
I think you maybe have set up something wrong in mainsettings (send mail options - many times you can leave those fields empty).
I can see you run an old version of Php-Fusion (v6.00.307). You should upgrade to the newest version (v6.01.6) as soon as possible to keep hackers out.