Certain addresses (hotmail espc.) unable to receive messages 2

[TimCHTECH]

We have a server running SBS 2003 with Exchange that is experiencing a weird problem. Users in the domain are able to use their exchange accounts to send and receive email perfectly in almost all cases except a few, any time one of them tries to send an email to certain large free email providers (Yahoo, Hotmail, etc) the message appears to send just fine, going through the outbox in to the sent folder with out any errors, but the free email accounts will never receive the message. The accounts are able to send to the exchange accounts but any replies are not being received. Any ideas? Like I said, there are no error messages being generated, and everything "appears" to be working correctly.

 

[xmsre]

No PTR record in your external DNS.

 

[TimCHTECH]

Thanks for your response, unfortunately I'm not quite sure what you mean. Can you be a little more specific?

 

[darren97]

You need to get the people who provide your isp to setup a ptr record for your mailserver. check out

http://www.dnsreport.com

type in your e-mail domain name and look under the section 'reverse dns entries for mx records' If the e-mail says its coming from mail.yourdomain.com but the there is no ptr pointing back to your mail svr then hotmail etc will not accept it.

 

[TimCHTECH]

Bingo!

FAIL - Reverse DNS entries for MX records
ERROR: The IP of one or more of your mail server(s) have no reverse DNS (PTR) entries.

I'll contact the ISP and see if we can get this resolved, thanks a lot for your help guys!

 

[Knutern]

Very interessting reading this thread, because we had until recently no PTR-record, but still we were able to send e-mails to hotmail.com.

Maybe hotmail just implemented PTR-checking.

Cheers
Knutern

 

[xmsre]

Around the end of the year.

 

[TimCHTECH]

Just an update, after getting reverse DNS set up at the ISP we were still unable to send emails to Hotmail, Yahoo and other email hosts. After doing some further investigation we determined that our Exchange server was being used as a relay host and that certain SMTP connector queue's (such as Hotmail, Yahoo and such) were just overloaded with thousands of messages waiting delivery, after following KB Article 324958 we were able to get it all cleaned up and working correctly. Anyone else who is having a similiar problem should probably look in to this as a cause.

Thanks for the help everyone!