my php mail function is not sending delevering mails in yahoo -

In this way I have used the mail function in php. Everything is fine for Gmail; It's being delivered to Inbox, but it's not delivering in Yahoo.

  if (isset ($ _ POST ['send'])) {$ uname = $ _ POST ['username']; $ Mailid = $ _ post ['mail']; $ Theme = "is"; $ Mail = "myyahooid@yahoo.com"; $ SendMessage = $ _ Post ['SendMessage']; $ Headers = "to:" $ Melid "\ N"; $ Headers = 'MIME-version: 1.0' ?? ². PHP_EOL '; $ Headers = 'Content-type: text / html; Charset = iso-8859-1 '. PHP_EOL; $ Mail_sent = Mail ($ Mail, $ theme, $ sent message, $ header); If ($ mail_sent) resonates "thanks"; The second "request unsuccessful" echo; }   
 I do not know where the problem is, when I send it to Yahoo, it is giving me success message but is not distributing it.   
 
 
  Message Filtering Settings  -  
 Change -  
  $ for headers. = 'MIME-version: 1.0â ?? ². PHP_EOL ';   
  
  $ headers = 'MIME-Version: 1.0'. PHP_EOL;