How to Verify an SMTP Virtual Server Is Not Set to Open Relay
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How to Verify an SMTP Virtual Server Is Not Set to Open Relay
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How to Verify an SMTP Virtual Server Is Not Set to Open Relay
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To configure your SMTP virtual server to receive Internet mail, you must perform the following tasks:
Configure the inbound port as 25 and specify the IP address
Other servers on the Internet expect to connect to your SMTP virtual server on port 25. By default, all SMTP virtual servers use this port. For detailed instructions, see .
Verify that your SMTP virtual server allows anonymous access
To receive Internet mail, your SMTP virtual server must permit anonymous access. Other servers on the Internet expect to communicate anonymously with your SMTP virtual server to send Internet mail to your users. For detailed instructions, see .
Verify that default relay restrictions are configured on your SMTP virtual server
By default, the SMTP virtual server allows only authenticated users to relay e-mail messages. This setting prevents unauthorized users from using your Exchange server to send e-mail messages to external domains. For detailed instructions, see the procedure below.
In Exchange System Manager, in the Properties dialog box of the SMTP virtual server, on the Access tab, click Relay.
In the Relay Restrictions dialog box (see the following figure), select Only the list below (if it is not already selected), click Add, and follow the instructions to add only those hosts that you want to allow to relay mail to the list.
If you select All except the list below, unauthorized users might access your server to distribute unsolicited e-mail messages on the Internet.
Relay Restrictions dialog box
Select Allow all computers which successfully authenticate to relay, regardless of the list above (if it is not already selected).
This setting allows you to deny relay permissions to all users who do not authenticate. Any remote Internet Message Access Protocol version 4 (IMAP4) and Post Office Protocol version 3 (POP3) users who access this server will authenticate to send mail. If you do not have users who access this server through IMAP4 or POP3, you can clear this check box to prevent relaying completely, thereby increasing security. You can also designate a specific server for IMAP4 and POP3 users, and then clear this check box on all other Internet gateway servers.
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Godaddy免费邮箱申请与使用和解决Godaddy主机SMTP发信问题
& 日 17:25 &
Godaddy免费邮箱也就是Godaddy域名邮箱，或者按照国内习惯说法是企业邮局，类似于国内的、等，可以用自己的域名作为邮件的发件人，这样可以明显区别于一些个人的免费邮箱，特别适合企业使用。
在Godaddy购买域名或者空间时都会赠送一个，购买域名会送一个1GB的邮局，购买空间会送一个100MB的邮局，目前Godaddy的邮局机房和它的主机一样共有美国、欧洲和亚太三大机房。
Godaddy免费邮箱也是一个朋友留言提醒部落给大家分享一下的，有些朋友一直在使用一些免费的邮局服务，经常不地稳定，Godaddy的邮局服务是购买域名送的，尤其适合用来和美国广告联盟或者经理们交流。
说起Godaddy免费邮箱，就又让人想起主机无法使用SMTP发信的问题，虽然Godaddy支持用PHP邮件函数来发信，这也是Wordpress等默认的发信方式，但是还是有人想用SMTP来代替PHP发送邮件，好处是可以自定义发件人和防止被判定为垃圾邮件。
经过测试Godaddy主机已经禁用了大部分的第三方SMTP，只能使用Godaddy主机自己的SMTP，当然这个是免费的。由于申请了Godaddy免费邮箱，我们还可以用Godaddy的免费邮箱来用作SMTP发信，成功解决无法使用的问题。
这里还有一些邮箱实用性的文章，可参考：
1、解决垃圾邮件：
2、访问Gmail：
3、免费一年邮局：
Godaddy免费邮箱申请与使用和解决Godaddy主机SMTP发信问题
一、激活开通Godaddy免费邮箱服务
1、首先是进入Godaddy用户管理中心，然后在“Email”中可以看到可申请的免费邮箱。
2、点击下面的设置，会弹出要你选择设置Godaddy免费邮箱的页面，免费空间是送100MB容量的邮箱。
3、免费域名会送一个1GB容量的邮箱，可选美国、欧洲和新加坡三个机房地点。
4、确认后可以看到成功开通Godaddy邮箱的提示。
5、返回到邮箱列表中，点击后面的“Launch”按钮即可进入邮局管理中心。
二、创建和管理Godaddy邮箱账号
1、进入到了邮箱管理中心后，先点击新建一个新的邮箱。
2、填入你想要注册的邮箱账号，然后是设置密码，点击创建。
3、创建好了邮箱账号后，可以返回管理已经创建的邮箱，可编辑、删除和修改邮箱密码等。（点击放大）
三、配置DNS记录建立自己的邮局服务
1、点击“Tools”中的“Server Setting”。
2、这里可以查看到自己的邮局MX记录和CNAME记录。
3、到域名DNS管理处，将域名的MX设置为刚刚显示的，我的是：smtp.secureserver.net和mailstore1.secureserver.net。
4、待MX生效后，我们就可以点击邮箱账号后面的“Launch”，启动进入邮局管理中心了。
5、这就是Godaddy免费邮箱的管理页面，和一般的邮箱都差不多，有收件箱、草稿箱、邮箱容量等功能。
四、用Godaddy邮箱解决Godaddy主机SMTP发信的问题
1、Godaddy主机默认是可以用PHP邮件函数来发信的，这也是大多数程序所默认的，但是有时候我们可能要用到SMTP发信的方式。
2、部落在文章中就说到了用主机自带的PHP函数发信容易被各大邮箱判定为垃圾邮件，而用SMTP则没有这个问题。
3、经过测试Godaddy禁止了第三方的SMTP服务器，只能使用自己的SMTP服务器来发信，既然我们已经申请了Godaddy邮箱，那么就可以充分利用邮箱的SMTP发信了。
4、在Wordpress中安装，打开插件设置页面，SMTP Host填写：smtpout.secureserver.net，端口是80.
5、勾选“Use SMTPAuth”，SMTP Username中填写你的Godaddy邮箱账号，下方是密码，最下方的可以设置发件人和发件人名称。（点击放大）
6、设置完成后，点击测试是否可以正常用STMP发信。这是部落测试的结果，发件人和发件人名称都是我刚刚成功设置的。
五、不用Godaddy邮箱也可以解决Godaddy主机SMTP发信
1、上面我们用购买域名赠送的Godaddy邮箱解决了Godaddy主机的SMTP发信的问题，如果你没有Godaddy邮箱但是有Godaddy主机，又该如何解决SMTP发信呢？
2、其实Godaddy已经有了一个公共的SMTP的服务器：relay-hosting.secureserver.net，该服务器的端口是：25
3、我们在Configure SMTP插件中不要勾选“Use SMTPAuth”，其它的都不需要设置了，发件人和发件人名称依然可以自定义，保存后就可以直接使用SMTP发信了。（点击放大）
六、Godaddy免费邮箱使用小结
1、Godaddy免费邮箱由购买Godaddy主机或者域名赠送的，首次使用时需要到邮局那一栏中启用并设置好一个域名，同时做DNS解析就可以使用了。
2、Godaddy域名邮箱特别适合用作Godaddy主机上SMTP发信，当然Godaddy公共的SMTP服务器也可以直接使用，不过最好设置一下发件人，防止被误判为垃圾邮件。
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Document informationDocument ID:4541Subject:What is SMTP relayCreation date:12/14/15 4:35 PMLast modified on:12/14/15 4:35 PMWhat is SMTP relay?
Many administrators misunderstand the concept of SMTP relay. Some over-cautious administrators block SMTP relay completely and others leave it open for any Internet user to misuse their servers. Problems exist in both extremes. Therefore, it is important to understand exactly what SMTP relay is and how to configure your SMTP server so that is does not leave you vulnerable to outside attacks and allows legitimate users to send and receive emails. This article should clear up some of the confusion on this topic and show how to effectively turn off an open relay.
What is SMTP
Before we dive into SMTP Relay, it is important to know how the SMTP protocol works. SMTP is an acronym for Simple Mail Transfer Protocol. Most of Internet service providers nowadays use this protocol to send email. Email clients, also known as Mail User Agents (MUA), utilize this protocol and act as an SMTP client to distribute email messages to the recipients. When a MUA sends an email messages, it connects to the configured SMTP server and communicates to it using the SMTP protocol.
Internet mail works pretty much like our postal mail. When you wish to send a letter or a package via snail mail, you put the letter inside an envelope, write the recipient's as well as your return address and drop it off at your local post office. The local post office figures out the final destination of the package and sends it to the appropriate post office in the recipient's town. One important factor to notice here is that if both sender and recipient are in the same town no other post office gets involved.
Electronic mail works pretty much the same. SMTP servers act as local post offices. When a user wishes to send an email, he or she sends it to the SMTP server, which then forwards it to the recipient's SMTP server. Rather than street address and apartment numbers, electronic mail recipients are identified by unique email addresses. Every SMTP server is configured to handle one or more domain names. Analogous to snail mail, if both sender and recipient are in the same domain no other SMTP server gets involved.
Following characteristics are common between snail mail and electronic mail.
Every mail package is wrapped within an envelope that contains:
Sender's name and address.
Recipient's name and address.
Post office's stamp.
A timestamp when package was received.
Every electronic mail is wrapped within an envelope as well and contains:
Sender's name and email address.
List of recipients and their email address.
SMTP server's signature. There can be more than one SMTP server involved.
The date and time the email was received.
Electronic mail can have more elements than mentioned above.
There is no guarantee that the sender's name and address will always be correct. It is very easy to forge the sender's identity.
Similarly, it is very easy to hide the sender's true identity in an electronic mail.
If the sender and receiver are in the same town, your local post office will not send the package to any other post office.
If the sender and receiver are handled by the same SMTP server, no other server will get involved.
Although the sender's identity cannot be trusted, you can still find a few things about the package by looking at the envelope such as the town letter was mailed from and time.
Similarly, the SMTP envelope (also known as header) contains information such as sender's IP Address and date/time stamp the mail was sent.
Every post office is assigned a postal code or zip code, which is used to identify it location. It is possible that in one post office may handle multiple zip codes.These postal/zip codes are known as domain names in SMTP speak. Every SMTP server is configured to handle one or more domains. Domain name is the text that appears after the @ sign in an email address.
What is mail relay
In case of snail mail, the local post office is a government agency and there are no restrictions on who can send a package. Consider a scenario where you live in town A and you want to send a package to town B. When one town's post office accepts packages from another town it is said to "Relay" your message.
Similarly, if you work for company A and want to send an email to someone in company B, you connect to your SMTP server which then relays your message to the SMTP server owned by company B. The notion that an SMTP server accepts an email that is destined for a different SMTP server is called relaying.
It would be impossible to send email if every SMTP server in the world stopped relaying
User authentication
The electronic world is a bit different than the real world: you can do things faster, cheaper and distances do not matter. Imagine every time you wanted to send a snail mail you were asked to show your passport or any other document that proved your identity. This would add extra security at a cost of frustration and time. However, the frustration level associated with asking for a user's id and password in an electronic transaction is much lower than the burden of having to carry your passport.
Most SMTP servers ask for the user's credentials in terms of their id and password. The SMTP server will allow users to relay their message to a different server only if these credentials are correct. This authentication mechanism ensures that no one outside the organization can use the company's SMTP server to send message to a third party recipient.
What is an open relay
Your server is said to be an open relay if it accepts messages on behalf of other domains and does NOT require user authentication. In the case of an open relay, a person sitting in Singapore can send an email to California through your server, which could be in London.
Open relay servers are frequently misused by spammers sending unsolicited emails. Once a malicious user finds out about an open relay server on the Internet, he/she can send millions of messages all over the world, potentially bringing your network to its knees.
Several organizations have setup databases of IP Addresses that list and track open relay servers. If you have an open relay server you run the risk of having your IP listed in one of these databases. As a result many SMTP servers may not accept emails from you.
How to check for open relay
The easiest way to test for an open relay is using
Alternatively, you can send an email specifying the test server as your SMTP server and without inserting a user id/password. This can be done via any User Agent, such as MS Outlook, Netscape Messenger or Eudora. In the configuration, specify the SMTP server that you want to test and remove any user id/password that you may have specified. Try sending emails to multiple domains and if the email is accepted your server might be an open relay.
User commentsPosted by Moziz on 5/28/13 4:32 PMWow. Finally a clear explanation. Thanks!Posted by Petarian on 4/29/12 12:05 AMFantastic article. Just wanted to thank Xeams team for this.Posted by
on 8/8/12 10:52 AMGreat article, but I have a question. If open relay servers can be so easily misused to attack other servers, why are there open relay servers in the first place?Posted by Diane on 7/7/13 2:03 PMVery useful.
Finally a simple yet detailed explanation... thanksPosted by Padma K on 6/15/14 1:16 PMWell written and simplePosted by jawahar on 12/25/13 1:13 AMThank you .Very clear and simple.But i want to know onething. What is the benefit with using SMTP server if we have exchange server in office?Posted by Micehelle Melee on 5/3/17 6:43 AMMost of the information being provided via this post is correct and valuable, however to those in the KNOW, there are still ways around it.
When it comes to Exchange EMail, a Microsoft propriety entity your information is incorrect. Posted by
on 10/17/13 5:44 AMGood article. Helped alot to understand SMTP relayPosted by Lavanya on 9/19/14 3:35 PMcool :) :) :)Posted by Kader on 4/3/14 9:48 AMcomplex issue explained with simple words in simple way
ThanksPosted by Heet on 4/24/14 4:44 AMThank you for such a simple yet truthful explanation with simpler example :) Really useful article.. Thumbs up for xeams team (y)Posted by Mueed on 11/21/17 11:35 PMGreat explanations are given in this article along with well know example to understand thing clearly. Thanks. Posted by Carol on 9/9/15 12:40 PMVery helpful - simple, concise explanation.
Perfect level of information I needed.
Thank you!Posted by Ian Hinson on 10/17/13 9:01 AMThis article fell short of what it promised to explain.
Starts out by telling us that some over-cautious admins block SMTP relay completely. but then goes on to explain that SMTP relay is just the benign process by which different SMTP servers communicate with each other, such that it would be impossible to send any emails with SMTP relay.
But then, if SMTP relay is essential to the process, how is that some over-cautious admins can &block SMTP relay completely& and then not notice straight away that no one is able to send emails to other email domains!?
Nope. There must be another explanation of what an SMTP relay is.Posted by zechariah kassa on 6/8/11 6:46 AMgood explanation of how smtp works.mostly the analogy , it is very clear thanksPosted by
on 5/16/14 1:14 AMuse full info thanks!!!!!!!!!Posted by
on 4/4/13 8:24 AMVery Good explanation with proper examples, which will help to understand......Thank you so much.
on 8/5/16 2:31 AMGreat Article. ThanksPosted by
on 4/2/12 5:14 AMGreat article!
Actually we need to send for maybe 10000 email address once every week, what service do your recommend us to use? We want to use the smtp settings in outook.
Thanks.Posted by naamila on 10/24/15 4:11 AMWow. Finally a clear explanation. Thanks! Surperb Thanks...!
Posted by Vignesh Lakshmanan on 4/22/15 7:55 PMThis was really helpful to understand what is SMTP.
Thanks a lot!Posted by Faizi on 1/19/16 5:40 AMYes it is great article,can you please add article how to configure secure relay server and what is its dependency.
ThanksPosted by G umapathi on 7/9/13 5:41 AMThanks!, that a great comparision.Posted by
on 1/14/13 10:13 PMGreat article.
It really gives you a great example and makes understanding very easy.Posted by CyberVerme on 2/1/15 7:02 PMThank you!
exactly what I needed.
Fantastic as explained a complicated thing with the example of the real mail.Posted by Alfonso on 5/17/13 7:32 AMNice article. A complex topic made easy. Thanks!Posted by Chintamani on 9/20/13 2:23 AMNice explanation with proper analogy. Thanks.Posted by satyanarayan on 8/24/14 10:07 AMNicely explained. Now the interesting part of 'how can someone misuse my mail server header' and make it become like an open relay or something like that' is forgotten. Have you mentioned it another article or something?
I have bookmarked this as favourite for it concisely explains the basic concepts well.
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