前段时间为了WordPress可以发送邮件折腾了一翻VPS，到今天才知道原来Vultr为了防止某些人滥发邮件默认关闭了SMTP所需要的25端口。当初还以为是自已的技术问题或是Plesk管理面板问题，最后选用了第三方SMTP插件方式实现。
对于有轻度强迫症的我，怎能容忍使用第三方插件来实现呢？于是马上邮件Vultr客服：
Please unblock port 25. WordPress need it open. Thanks!
很快收到了Vultr客服邮件：
Hello,
In order to combat spam and spamlike activities, our system requires a properly completed and vetted CC authorization form to confirmclients’ identities prior to SMTP block removal.
Please complete the authorization form and fax it in or scan and attach to this ticket:
https://my.vultr.com/billing/cc_auth_form.pdf
Regards, Eric Van Trease System Administrator
下载PDF文档一看，还要求挺高的。部份内容如下：
Please FAX the following information to 732-566-1268 or [email protected] for verification. International customers please FAX to +01 732-566-1268.
1. A copy of your government issued photo ID – driver’s license, passport, etc. (Please use a camera phone or digital camera to take a photograph)
2. A partial image of the card used to fund the account to ensure the provided identity matches the name printed on the card. For your protection, please cover all but the last 4 digits of the card.(Please use a camera phone or digital camera to take a photograph)
3. This completed form.
看来Vultr对于滥发邮件这个问题挺重视的，于是按照要求传真过去，处理速度非常快，十多分钟后处理完毕。但最后我还是使用第三方的SMTP服务器，因为测试得知使用VPS自带的SMTP端口进行邮件发送会暴露VPS的真实IP，虽然有方法可以处理，但懒得折腾了。以上就是Vultr开通SMTP所需的25端口整个过程，在此公布本次过程是以免大家像我之前那样折腾这个问题。
—2016-10-06更新
我今天按以上方案要求Vultr开通SMTP所需要的25端口，很快就收到邮件：
根据现在这种情况猜侧，如果是新用户不会轻易许可开放SMTP的25端口，老用户就不用了，发过邮件过去就解决了，然后重启VPS既可。当前，前提是已安装好mail服务。
