Cannot send e-mail to hotmail, yahoo, aol, etc...

We are running Exchange 2003 on Windows Server 2003

For whatever reason we have intermittant issues sending e-mail to these organizations.  The messages time out as non-deliverable.  The addresses are known good addresses.  I've check dns resolution through nslookup and can get to the mx records with no problem.  I can also telnet to the mx addresses on port 25 so I know the server addresses are good.

I've also ran our domain against serveral blacklist databases and we come up clean.  I've also verified that relaying is turned off.  

I have heard over the last few months that these organizations were going to implement an antispam system called SPF.

Question:  Are the service providers listed above using SPF or is there another issue at play?

Thanks in advance for the assist.
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SamuraiCrowAsked:
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BNettles73Commented:

I know AOL is in the process of setting up SPF and it has caused numerous headaches. To determine if it is an SPF type issue, I'd need to see the NDR failure notification. The NDR's generated due to these issues are a little bit different than the standard notifications.

That being said, you may look into the following solution - I've seen quite a few SMTP issues to yahoo, aol etc, be resolved by configuring an SMTP connector for these ISP's.

http://www.amset.info/exchange/smtp-connector.asp

Additionally, you need to make sure you have a reverse PTR record for your MX record.

Can you post an NDR that you are receiving?


Here is a link for AOL's SPF site ... it contains some info about some of the NDR failures you might see http://postmaster.aol.com/spf/
Here is a link about SPF if you haven't seen it ... http://spf.pobox.com/howworks.html
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SamuraiCrowAuthor Commented:
Here is one that I've received from Earthlink,  I'll post the others as soon as they are forwarded to me from the users:

-----Original Message-----
From: System Administrator
Sent: Thursday, September 09, 2004 9:04 AM
To: 'user@earthlink.net'
Subject: Undeliverable:RE: Howdy

Your message did not reach some or all of the intended recipients.

      Subject:      RE: Howdy
      Sent:      9/9/2004 9:03 AM

The following recipient(s) could not be reached:

      'user@earthlink.net' on 9/9/2004 9:04 AM
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            <servername.aknp.net #5.5.0 smtp;550-EarthLink does not recognize your computer (ip address) as connecting from an EarthLink connection.  If this is in error, please contact technical support.>

Thanks for the info.  I'll look into the links you provided and get back with you.
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BNettles73Commented:
Definitely check out this link http://www.amset.info/exchange/smtp-connector.asp ...
also - make sure you have the reverse PTR record setup for your MX record (this is a public dns record, not local, unless you host your own DNS)
you may also want to configure your virtual SMTP server to masquerade as whatever your MX record is, instead of replying as <servername.aknp.net> ... if your MX record is mail.aknp.net then you would configure that in the masquerade instead of using the FQDN .... does that make sense?
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SamuraiCrowAuthor Commented:
Sounds like a plan.  I'll make the modifications later tonight after the backups.  I'm pouring over the Amset site right now, looks like lots of good info.
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BNettles73Commented:

You can thank Sembee for that link later ... I saw him post it a few weeks ago I believe ... I've submitted the solution to 6 or 7 people since and seems like it works fairly well ...

we had a simliar issue with earthlink and aol but we ended up switching our DNS infrastructure to point to Microsoft's caching servers instead of using root hints ... this has worked fairly decent but the easier route seems to be using the SMTP connector ...
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SembeeCommented:
You can thank me for more than just the link... I wrote the page.

You can make the modifications live - if it doesn't work then the messages just sit in the queue. Adjust and then force the queues to try again.

That error message you got from Earthlink is very odd. You didn't try to enter Earthlink's SMTP server instead of the one from your own ISP (unless your ISP IS Earthlink)?

Simon.
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SamuraiCrowAuthor Commented:
Negative.  The message resulted from a reply to an email from Earthlink.  Earthlink is not our ISP.
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SamuraiCrowAuthor Commented:
Thanks for the prompt information and assistance.  It turns out that there were some internal issues as well as the ones that you pointed me to.
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