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Open Mail Relay-How to test

An open mail relay is an SMTP server configured in such a way that it allows anyone on the Internet to send e-mail through it, not just mail destined to or originating from known users.This used to be the default configuration in many mail servers; indeed, it was the way the Internet was initially set up, but open mail relays have become unpopular due to their exploitation by spammers and worms. Many relays were closed, or were placed on blacklists by other servers.[Wikipedia]

How to test your mail server for open relay:
1. At command prompt type:
C:/>telnet mailserver.yourdomain.com 25

220 mailserver.yourdomain.com ESMTP MAIL Service Version 6.0.3894 ready at Tue, 22 Aug 2011 05:22:00 -0700

2. helo

250 mailserver.yourdomain.com Hello

3. mail from: sender@otherdomain.com

250 2.1.0 sender@otherdomain.com....Sender OK

4. rcpt to: recepient@someotherdomain.com

250 2.1.5 recepient@someotherdomain.com

5. data

354 Start mail input; end with .

This is a test mail. Please ignore this-Nilesh

.

250 2.6.0 Queued mail for delivery

6. quit

221 2.0.0 mailserver.yourdomain.com Service closing transmission channel

Connection to host lost.

You have successfully sent an anonymous mail abusing open-relay.

But if you get 550 error like this:
rcpt to: recepient@someotherdomain.com

550 5.7.1 Unable to relay for recepient@someotherdomain.com
The mail server does not allow open relay and won't forward spam all over the net.








Comments

चंदन कुमार मिश्र said…
अच्छा। पढ़ा था ये सब।
September 15, 2011 at 7:20 PM
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