http://www.abuse.net/relay.html
Check that your server is not in ORDB.org Open Relay Database
Being safe from email-related threats have become a major threat in today’s broadband era. For years, computer specialists have been trying to prevent the proliferation of spam, email viruses, and other malware programs. According to these specialists, a secure network can prevent of the development of these unwanted threats. This can be achieved by checking your email relay setting.
How to perform an Email Relay Test
An outside individual who uses your mail server to deliver email using a false e-mail address is considered relaying mail via your server. A mail server that allows relaying is usually considered to be setup incorrectly and is frequently abused by spammers. These spammers find and use unsecured mail servers to send out unsolicited commercial email.
Tracking down a spammer who uses mail servers open to relaying is difficult. This is because the email appears to be coming from your server, rather than from the original sender. Such spam being delivered by your mail server can give your company a bad reputation.
How do you check your server for relaying? Easy, just use a computer outside of your organization and type the commands included in the tables below - you’ll want to do this from a command prompt.
In the following examples, mail.example.com is the mail server you are checking, sender@example.com is a valid e-mail account at mail.example.com (or a fake e-mail address - try both), and youremail@outsideaddress.com is the e-mail account you want this message to go to.
The parts you type are show in the table blow and replies from the server are shown to the right. This is an example of a mail server that does NOT allow relaying.
| You type this text | Server should respond with this |
| TELNET mail.example.com 25 | Trying 10.10.10.1. Connected to mail.example.com. Escape character is ’^]’. 220 mail.example.com |
| HELO mail.example | 250 OK |
| MAIL FROM: | 250 OK - Mail from |
| RCPT TO: | 550 Relaying is prohibited |
| QUIT | 221 Closing connect, good bye |
This is an example of a mail server that DOES allow relaying.
| You type this text | Server should respond with this |
| TELNET mail.example.com 25 | Trying 10.10.10.1. Connected to mail.example.com. Escape character is ’^]’. 220 mail.example.com |
| HELO mail.example | 250 OK |
| MAIL FROM: | 250 OK - Mail from |
| RCPT TO: | 250 OK |
| DATA | 354 End data with |
| From: sender@example.com To: youremail@outsideaddress.com Subject: Relay test This is a relay test and only a test. (type . or [enter].[enter] to end data) | 250 OK: Queued as T22122A5 |
| QUIT | 221 Closing connect, good bye |
How do you prevent message relay?
Before you start, check which version you are running - you must be running Microsoft Exchange Server 5.5 or greater, then follow these 7 steps.
1) Go to the Internet Mail Service Properties dialog box in Microsoft Exchange
2) Select the Routing tab at the top.
3) Select the option Reroute incoming SMTP mail (required for POP3/IMAP4 support).
4) Reroute incoming SMTP mail.
5) For each domain you host, you need an entry in the Routing section.
6) Click the Routing Restrictions button.
7) Make sure Hosts and clients with these IP addresses is checked. Leave the list of IP addresses blank.
Updated On: 12.07.11