SMTP communication error 5.1.0 address rejected

It isn't clear from your question this is occurring?

Is it when you are sending email to external email addresses?
Or is it happening when your own staff are sending email through your server?

Simon.

Some External addresses only.
I am thinikng may be rverse lookup

Do you think this error could be due to reverse lookup?

If your server has "AMExchFE.americas.ad.domain.com" as its SMTP banner, then that can cause some rejects.
Lack of reverse DNS may also cause a problem.

Take a look at my dns config page:
http://www.amset.info/exchange/dnsconfig.asp

and make sure that everything is set correctly.

Simon.

Thank you Sembee.... so should the server domain.com  or mail.domain.com  

You need to enter whatever the server is known as on the internet. "domain.com" is bad practise, an MX record should always be a host - so if the MX record is mail.domain.com then that is what you enter in to the FQDN, PTR records etc.

Simon.

This is what I did. I am still seeing the error message right after the message is sent?


The following recipient(s) could not be reached:

      joe jacob on 7/17/2006 10:23 AM
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            <exchange.mydomain.com #5.5.0 smtp;550 #5.1.0 Address rejected.>

I see the block I received from a new ISP listed in BLARSBL
[should not be used]  LISTED (127.3.0.0)    which is not an official one... Could that be the reason... However my server forwards to a smart host which should bypass that. right?

Do you get the message on all emails that are going out?
If so, then I would have to suspect the smart host is rejecting the email message.

Simon.

So you do not think it is a DNS issue or anything like that right.... as I was able to surf the net and go to many sites on the exchange server.
initially I did not have the smart host configured, but then I had to put it to the smart host as I figured this would be the problem why I could not send..... some messages go through to the external domains, but somethimes they do not and I get the failure... it is to all external domains if not most.

As you are using a smart host, whether it is all email or just some makes a very big difference.

What does message tracking show? Does it show the message as being delivered to the smart host correctly?

Simon.

I am using smart host, tried without it but still samething. All emails. However if you keep resending it would make it through

Can I clarify something?

It isn't 100% clear what is actually happening.
In your original question you said...

"I am getting this error message when users are trying to send to external addresses (they are authenticating to the server before sending is checked)"

Does that mean that this problem is affecting clients who are not using a MAPI client, but are configured as POP3/SMTP?

If you are getting the same message whether you are using a smart host or not, would tend to indicate that problem is local, or that you have a smart host configured elsewhere and are not removing it in the correct location.
For example, I have seen people configure an SMTP Connector to use a smart host, forgetting that there is already a smart host configured directly on the SMTP virtual server. A smarthost configured in that location would override whatever is in the SMTP Connector.

You need to see what server the messages are being delivered to, and only message tracking will tell you that.

Simon.

Thank you sembee..... it was spam.... the provider Sprint gave us a subnet that was black listed on RBLs. I pointed it to a mail relay gateway and added it to a relay list and worked around it this way..... sucks haa.

please look at this question as I would like to get your input on this one please.

sorry here is the question
https://www.experts-exchange.com/questions/21923868/Exchange-2000-offline-defrag-of-1-store-while-2-stores-online.html