首先你需要先到从http://glob.com.au/sendmail/下载sendmail.zip文件，点此可以直接下载噢，然后把它解压到如D:\php\sendmail\目录下。
然后打开php.ini文件，找到下面这段代码
[mail function]
; For Win32 only.
SMTP = localhost
smtp_port = 25
; For Win32 only.
;sendmail_from = [email protected]
; For Unix only. You may supply arguments as well (default: "sendmail -t -i").
; 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 =
默认情况下是以本机做为邮件服务器，这里我们需要借用sendmail来发送邮件，用sendmail来配置如用qq、163的邮箱来发送(一般都是以这种方式)所以我们需要把所有的选项都注销，即把SMTP = localhost和smtp_port = 25前面加上";"然后把sendmai_path=""前面的";"删掉，改为sendmai_path="d:\php\sendmail\sendmail.exe -t"，改完后的即是
[mail function]
; For Win32 only.
;SMTP = localhost
;smtp_port = 25
; For Win32 only.
;sendmail_from = [email protected]
; For Unix only. You may supply arguments as well (default: "sendmail -t -i").
sendmail_path = "d:\php\sendmail\sendmail.exe -t"
; 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 =
注意以上只需要开启sendmail_path即可，然后保存
接着修改sendmail目录下的sendmail.ini文件，主要填的内容有以下几项
smtp_server=smtp服务器地址(如 smtp.ym.163.com)
auth_username=邮箱登录名(如 [email protected])
auth_password=邮箱密码(如 xxxxxx)
force_sender=发件人地址全写(如 [email protected])
另外还有一项
; auto = use SSL for port 465, otherwise try to use TLS
把前面的";"删除，即开启SSL安全登录选项即可
以上四项正确填写修改完成后保存，然后重启IIS即可正常使用。
如果不能发送邮件，检查下端口是不是被屏蔽了，mcafee是不是设置了禁止发送邮件等