SMTPDiag Expected "250" error

Hello,
This one is driving me crazy.  I'm not sure when this problem started.  We have 2 ISPs, Earthlink's T1 service and a local broadband provider.  I receive the same error through both ISPs, which leads me to believe it's some type of reverse DNS problem.  However, I do have valid Reverse DNS entries setup for both ISPs ... mail.mydomain.com.  A reverse DNS lookup on both my IPs resolves correctly.

The error I get is this:
Error: Expected "250".  Server rejected the recipient address.  Failed to submit mail to mx.mc.surewest.net.

The email address we're trying to send to is another domain, not surewest, so I'm guessing Surewest is their ISP and they host their own server on the Surewest network.

The mail doesn't bounce back and doesn't make it to the recipient.  In the past, these emails have bounced back weeks or months later.  Our Exchange is set to deliver NDRs if messages are delivered in 3 minutes, so something weird is happening.

I contacted Surewest, and they pretty much told me to call my ISP.

As a test, I just tried an SMTPdiag to yahoo.com domain, and I am also getting a failure:
Error: Expected "220". Server is not accepting connections. Failed to submit mail to c.mx.mail.yahoo.com.

Any help is much appreciated!  Thanks.
LVL 1
BigFunkyChiefAsked:
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kieran_bCommented:
OK, lets try and emulate what SMTPDiag is doing to figure out what is going on.

On the Exchange server, Start > Run > telnet c.mx.mail.yahoo.com 25 > then issue commands as follows, and let us know where you get stuck;

ehlo yourdomain.com
mail from:you@yourdomain.com
rcpt to:someone@yahoo.com
data
subject:this is a test
whatever, blah blah blah
.

I expect that you are either on a bad IP, have a poor PTR record or an incorrect SMTP greeting - so you could check that out too by putting your domain into -> http://www.dnsreport.com

Kieran
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BigFunkyChiefAuthor Commented:
Thanks for the reply.  Actually the Yahoo eventually went through, and my main concern is the surewest issue, so here's what happens when >> telnet mx.mc.surewest.net:

220 rg3.mc.surewest.net ESMTP Mirapoint 3.8.4-GA; Mon, 1 Feb 2008
EHLO mydomain.com
250-rg3.mc.surewest.net Hello mail.mydomain.com [xxx.xxx.xxx.xxx] (may be forged), pleased to meet you
250-8BITMIME
250-SIZE 31457280
250-DSN
250-ETRN
250-AUTH LOGIN
250-AUTH=LOGIN
250 HELP
mail from: myboss@mydomain.com
250 myboss@mydomain.com...Sender ok
rcpt to: client@clientsdomain.com
550 client@clientsdomain.com...Relaying denied

0
kieran_bCommented:
That looks like a recipient problem

Try putting the recipient email address here and seeing if you get the same problem -> http://www.zmailer.org/mxverify.html

Kieran
0

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BigFunkyChiefAuthor Commented:
Yup, same thing:
 550 <client@clientsdomain.com>... Relaying denied


Something WRONG!! rc=550
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kieran_bCommented:
Then it is a recipient problem - nothing to do with you.

Do you have any other problem domains?
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BigFunkyChiefAuthor Commented:
I just called the client, of course they think everything is working great.  I had her send me a test email, and it came through, I replied and she got it, and replied back confirming.

My issue is my boss has been sending emails to this company and the guy doesn't receive them at all.  I had other issues sending to Surewest, so thought the SMTPDiag was showing me a problem going to that domain.  Now I wonder.  But if I can send mail to the user, shouldn't SMTPDiag show successful, at least occassionaly?
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kieran_bCommented:
Yes it should show successful, but I am wondering - if a reply works, can you confirm that you are entering her address correctly?
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BigFunkyChiefAuthor Commented:
Regarding other problem domains, there was one other one that my boss mentioned. I'll need to get it and test.

DNSReports tells me:
[ERROR: A CNAME appeared in the MX records; this is not valid (per RFCs 974 "Minor Special Issues" section, and 1034 section 3.6.2.
          Mailservers are not required to send E-mail to mail.clientdomain.com.]
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kieran_bCommented:
That dnsreport error is just telling you to remove the CNAME from the MX records - it is a minor error.  Something that should be fixed, but not a deal breaker.
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BigFunkyChiefAuthor Commented:
Weird.  Now everything passes, no problem!  I have no idea why it's now working..I have not changed anything.  Anyways, thanks for all the help, points awarded.
0
kieran_bCommented:
I expect it was a problem on their end, and they resolved it and covered it up - that is just a wild guess though
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BigFunkyChiefAuthor Commented:
And from the remote site, it now passes occassionally, and then gives an 451 Requested mail action not taken: mailbox unavailable error.  Strange.  Thanks again for the help.
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kieran_bCommented:
451 is a temp error, usually meaning they are using greylisting.
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