Problems sending email from Exchange 2000 to Yahoo account

I have an internal and external email address. I'm on Exchange 2000. When I send an email to the external address, a non-delivery report (NDR) error message is returned. I created an SMTP connector, but continue to get these NDRs. My DNS is OK and I don't have a domain name.

Example

My Outlook profile has two accounts:

xxxxx@domain.local (default profile)
yyyyy@hotmail.com

  1. I create a new message to yyyyy@yahoo.com.

  2.  

  3. I receive a message reply by the administrator because Exchange does not know 'yahoo.com.'

Why is this happening? What could be going on?

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You are not alone in this problem. Chances are, you have a third-party spam filter running at your organization. Almost every spam filter today is blocking yahoo.com and other ISP mail domains because they do not register a reverse DNS entry (PTR) that 100% matches their customers' email addresses.

For example, I found that a reverse lookup of one of the yahoo.com mail server's IP addresses returned a domain of servername.mail.yahoo.com as opposed to just servername.yahoo.com. This is close but maybe no cigar for your filters.

In the case of some other ISPs that are being blocked, it is not even close at all. The bad news is that, if you set up an exception for the entire yahoo.com domain, a lot of spam will come through unchecked. If you leave it blocked, you will continue to have this problem.

I think the solution probably lies with yahoo.com and other ISPs.

Do you have comments on this Ask the Expert Q&A?Let us know.

This was first published in March 2005

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