Home Backend Development PHP Tutorial PHP发送邮件方法详谈

PHP发送邮件方法详谈

Jun 20, 2016 pm 01:03 PM

网站应用中向客户发送邮件是常见的一个功能。SMTP协议貌似简单,而且资料繁多,但要彻底搞清楚客户端服务器之间的身份和关系处理,也不是件容易的事。

       本文简明扼要对smtp交换过程中身份和条件进行说明,使初次接触smtp开发的能有个清晰的处理思路。错误之处请多指正。

       先说说smtp的基本原理, 邮件客户端(outlook)和发送方smtp服务器之间,  发送方smtp服务器和接受方smtp服务器之间,走的都是smtp协议.

       先说说我们最常见的情况:用outlook发邮件,从 admin@scutephp.com 发往 to@scutephp.com。 outlook里写好邮件后发送,会连接到帐号里登记的smtp服务器25端口,开始smtp会话:

mail from:
       admin@scutephp.com服务器发现邮件的mail from 是本域的(linuxidc.com),这种情况下smtp服务器一般需要验证用户身份,验证通过提交邮件,邮件进入服务器的发送队列。 服务器投递邮件的进程或线程,扫描发送队列,取出邮件后分析要往哪发。 服务器发现邮件是发往 linuxidc.net,不是本域,先通过dns服务器查询 to@scutephp域的mx记录,假设为 smtp.scutephp.com,邮件投递进程连接 smtp.scutephp.com 的25端口,开始smtp会话

mail from:

       scutephp.com服务器判断邮件是来自别的域,发往本域,所以不需要验证用户。不过有可能的情况是scutephp.com服务器先检查一下发信服务器的ip地址,和mail from 里的域名对应的mx记录是否匹配,不匹配的拒收。如果没有符合什么拒收条件,那么scutephp.com手下这封信,放入rose的邮件夹,rose可以通过pop3收取邮件。

       如果 scutephp.com发送邮件失败的话,邮件进入发送失败队列,可能直接扔掉,或者再试着重发n次,如果都不成功,会通知发件人或别的什么,这要看服务器的处理。

       现在再说说php发邮件,首先要搞清楚,要用什么身份发送邮件。第一种:把自己当作outlook之类的客户端,先连到发信服务器,提交邮件后让发件服务器往外发送。第二种:把自己当作发信服务器,直接通过smtp连接收件人的服务器发送邮件。

       这里我不推荐第二种方式,原因是:如果你php所在服务器的域名,ip,mx记录没有严格设置好的话,一般收件服务器有很大的几率会拒收;发送邮件本身的传输过程时间无法控制,如果和收件服务器有很大的延时,会严重影响自己的web服务器的工作,另外也不具有失败重发等处理。

       对于发送邮件,windows和unix和很大的差别。windows一般来说都是像outlook那样的方式,用smtp协议连到发件服务器发送邮件。unix有自己的传统方式,就是unix主机自带 smtp server,传统的就是sendmail。另外还有个“sendmail”的概念,这里说的是一个程序的名字,无论是sendmail,qmail,postfix等等,都提供这个命令程序,通过它,可以把邮件放入本地邮件发送队列,让sendmail,qmail,postfix之类的投递程序去投递发送。sendmail程序一般是从标准输入里读入邮件内容。php的mail()函数实际上会打开sendmail程序,通过标准输入把邮件内容传给它,由sendmail程序来发送,剩下的就不管了。

       所以大家可以看到,php里关于mail() 这个函数的说明,如果是在windows上,一般是设置 php.ini里 SMTP 和 smtp_port 选项的值,通过类outlook客户端的方式发送,但是这种方式的致命弱点是不支持smtp验证,而现在邮件服务器基本都是需要smtp验证的。uxni下一般需要设置 sendmail_path ,来说明sendmail程序的路径。当然windows上也可以用sendmail程序发送。

       如果是unix,最理想的情况是,你的php所在的web服务器本身也是个smtp server,并设置好了mx记录等等,或者你有个能发送邮件的sendmail程序(自己写,封装smtp发送)那么先配置好 php.ini 里的sendmail_path,通过mail()函数就直接发送了。

       如果没有能用的sendmail程序,那么就要通过socket 用smtp协议发送了,php这方面有很多扩展的库,可以直接拿来用。建议连上一个服务器让他帮你发,不建议直接连收件服务器(原因前面说了)。这里还有就是不建议直接在网页上php里连接发送,推荐的方式是把邮件写到数据库或文件里,让另一个程序(php,perl,python 都可以写)扫描后通过sokcet连接发送。这样既给用户有了好的响应体验,也可以控制发送的过程。


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