'[Modify] the php.ini file to use it (commented out the other lines):

'[mail function]
'; For Win32 only.
'; SMTP = smtp.gmail.com
'; smtp_port = 25

'; For Win32 only.
'; sendmail_from = <e-mail username>@gmail.com

'; For Unix only. You may supply arguments as well (default: "sendmail -t -i").
'sendmail_path = "C:xamppsendmailsendmail.exe -t"

[sendmail]

smtp_server=smtp.gmail.com
smtp_port=25
error_logfile=error.log
debug_logfile=debug.log
auth_username=<username>
auth_password=<password>
force_sender=<e-mail username>@gmail.com'

'Warning: mail(): SMTP server response: 421-4.7.0 [14.200.59.18 15] Our      system has detected that this message is 421-4.7.0 suspicious due to the very low reputation of the sending IP address. 421-4.7.0 To protect our users from spam, mail sent from your IP address has 421-4.7.0 been temporarily rate limited. Please visit 421 4.7.0 https://support.google.com/mail/answer/188131 for more information. c185si2211020itg.117 - gsmtp in C:Program Files (x86)EasyPHP-Devserver-16.1eds-wwwintroducingphpCode Work phptestmail.php on line 10
Check your email now....'

<?php
ini_set("SMTP", "aspmx.l.google.com");
ini_set("sendmail_from", "my_email@gmail.com");

$message = "The mail message was sent with the following mail     setting:rnSMTP = aspmx.l.google.comrnsmtp_port = 25rnsendmail_from = my_email@gmail.com";

$headers = "From:my_email@gmail.com";


mail("to_email@yahoo.com", "Testing", $message, $headers);
echo "Check your email now....<BR/>";
?>