test email The specified string is not in the form required for an e-mail address.

hi
i can see the mails are arriving to the queue but no mail are sent

the service is runnig

test mail is not working   - i get "The specified string is not in the form required for an e-mail address."

i double checked all the settings , looking for blanks etc  
in the system log i can see the same error message

thanks
Nir