551 This is not a relay host - mail must be to or from host domain

[cyberslee]

Hello,

I am getting this message from one doamin: smtp.schooldude.com.

I have spoke to schooldude and they are telling me that I am blocking their domain. I am not blocking any domain at the firewall level.

Here is the message I get:

-----Original Message-----

From: Mail Delivery Subsystem [mailto:MAILER-DAEMON@smtp.schooldude.com]

Sent: Wednesday, June 02, 2004 11:15 AM

To: Richard Kaz

Subject: Returned mail: response error

The original message was received at Wed, 02 Jun 2004 11:15:02 -0400

----- The following addresses had permanent fatal errors -----

<kzimmerm@nburlington.com>

<dczehut@nburlington.com>

<rkaz@nburlington.com>

----- Transcript of session follows -----

... while talking to firewall.nburlington.com

>>> RCPT To:<rkaz@nburlington.com>

<<< 551 This is not a relay host - mail must be to or from host domain.

Thank you for all your help!!!

Steve,

[mostiguy]

The mx records for nburlington.com are:

Non-authoritative answer:

nburlington.com MX preference = 0, mail exchanger = firewall.nburlington.com

nburlington.com MX preference = 10, mail exchanger = mail5.nburlington.com

firewall.nburlington.com internet address = 209.158.102.5

Why is your environment attempting to send mail for them to smtp.schooldude.com?

I was able to successfully telnet to the smtp port of firewall. , but mail5 does not seem to exist.

[cyberslee]

Thanks for your reply..,

Can you please tell me who you referring to "them" when you asked "Why is your environment attempting to send mail for them to smtp.schooldude.com?"

I am new at this email stuff with firewall.

Thanks..,

Steve,

[sachin]

Hi,

This one is not the PIX firewall problem.This is the behaviour of Mail server.Your mail sever is validating the MX record for domain "schooldude.com"

MX record for schooldude.com.is "inbound.electric.net" which is schooldude.com Mail server. But they do have one more SMTP server which "smtp.schooldude.com".For this SMTP server they donot have MX record in their DNS server.So when mail comes to your domain from server "smtp.schooldude.com", your mail server rejects the mails from "smtp.schooldude.com" server as this one is not Mail exchanger for their domain.

I think your mail server is validating the sender's Mail server.So ask schooldude.com why mails are coming from smtp.schooldude.com ? why they dont have MX record in their DNS ? or change settings in ur Mail server ?