好多人在用php的mail()函数发送邮件时不成功，折腾半天也没找到什么问题。
我昨天也遇到这情况了，现在记录一下，以便以后再遇到这问题。
1:要用mail首先你要把sendMail扩展打开，我用的phpstudy，打开很简单，把勾打上就可以了。
2:然后打开php.ini然后搜索“[mail function]”，找到下面文本块，把我加红加粗的前面的;去掉，然后修改成你的邮件服务器，我用的163的，qq的比较麻烦，所以用的163。
sendmail_path="D:\phpStudy\tools\sendmail\sendmail.exe -t"
//这个后面的地址就是你的sendmail.exe的地址，如果你配置php环境时没有安装直接下载sendmail安装一下就可以了。
; For Win32 only.
; http://php.net/smtp
SMTP = smtp.163.com
; http://php.net/smtp-port
smtp_port = 25
; For Win32 only.
; http://php.net/sendmail-from
sendmail_from = intrwins@163.com
; For Unix only. You may supply arguments as well (default: "sendmail -t -i").
; http://php.net/sendmail-path
; Force the addition of the specified parameters to be passed as extra parameters
; to the sendmail binary. These parameters will always replace the value of
; the 5th parameter to mail(), even in safe mode.
;mail.force_extra_parameters =
; Add X-PHP-Originating-Script: that will include uid of the script followed by the filename
mail.add_x_header = On
sendmail_path="D:\phpStudy\tools\sendmail\sendmail.exe -t"
3：配置sendmail.ini
然后找到你的sendmail文件夹，找到sendmail.ini文件，搜索“[sendmail]”，配置相关信息。
4：同样的设置一下，看红色加粗部分POP3_这三个是设置接取邮件的配置，需要的也可以设置下，我们现在设置的是发送的配置。
smtp_server=smtp.163.com
; smtp port (normally 25)
smtp_port=25
; SMTPS (SSL) support
; auto = use SSL for port 465, otherwise try to use TLS
; ssl = alway use SSL
; tls = always use TLS
; none = never try to use SSL
smtp_ssl=auto
auth_username=****** //你的用户名
auth_password=********** //你的邮件密码
; if your smtp server uses pop3 before smtp authentication, modify the
; following three lines. do not enable unless it is required.
pop3_server=
pop3_username=
pop3_password=
; force the sender to always be the following email address
; this will only affect the "MAIL FROM" command, it won't modify
; the "From: " header of the message content
force_sender=intrwins@163.com
5：重启你的php环境，然后再试试应该就可以了。
<?php
$to = "zzndc@qq.com";
$subject = "我就是在测试php的mail函数，请163别给我退回";
$message = "我就是在测试php的mail函数，请163别给我退回";
$from = "intrwins@163.com";
$headers = "From: $from";
if(mail($to,$subject,$message,$headers)){
echo "发送成功";
}else{
echo "发送失败";
}
?>
