sendmail and php mail() - "no recipients found" -

I have installed sendmail on my Apache server (Ubuntu)

Everything seems to be that searching except for an email is not working, while PHP mail (); I have not received any error using

:

/ usr / sbin / sendmail: no recipient was found

It is in such a way that I am using the function:

  $ user_email = "myemail @ gmail.com"; $ Header = 'mime-version: 1.0' "\ r \ n"; $ Headers = 'Content-type: text / html; Charset = ISO-885 9-1 '"\ r \ n"; $ Headers = 'To:' $ User_email "\ r \ n"; $ Headers = 'To: minddom & lt; Do-not-reply@mydomain.com> ' . "\ R \ n"; Mail ($ user_email, "topic", "message", $ header);    
 
 
  $ user_email = myemail@gmail.com   
 should be  
  $ user_email = "myemail@gmail.com";