Which man sent an email using php + smtp? Please advise the solution

Which man sent an email using php + smtp? Please advise if sendmail is installed on my server and can be sent via mail for testing. why is the third time qq received a spam email? 163 cannot receive? Why? & Lt ;? Php $ to = & quot; test ***** @ qq.com & quot; $ Has the subje man sent an email using php + smtp? Please give me some advice
My server is installed with sendmail, which can be sent by mail. test, the third time qq received is in spam mail? 163 cannot receive?
Why?

$ To = "test ***** @ qq.com ";
$ Subject = "Test mail ";
$ Message = "Hello! This is a simple email message .";
$ From = "test ***** @ qq.com ";
$ Headers = "From: $ from ";
Mail ($ to, $ subject, $ message, $ headers );
Echo "Mail Sent .";
?>

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Yes. It indicates that there is no problem with sending emails, and may be intercepted by 163. Multiple tests.
------ Solution --------------------
If you use the sendmail service that comes with the system, spam is suspected. It is best to use third-party smtp for sending. There are many open-source libraries on the Internet.