Urgent:Exchange 2007 Not Sending Email

All this is urgent please help. While applying patches tonight I rebooted my exchange 2007 server and now I don't seem to be able to send messages to certain outside domains.

Delivery has failed to these recipients or distribution lists:
User One
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.

The following organization rejected your message: nlpi136.prodigy.net.
Sent by Microsoft Exchange Server 2007

Diagnostic information for administrators:

Generating server: server-v.domain.com
nlpi136.prodigy.net #550 5.7.1 Connections not accepted from servers without a valid sender domain.nlpi136 Fix reverse DNS for ##
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suriyaehnopConnect With a Mentor Commented:
"Fix reverse DNS for ". Could you check with them if they enable reserve dns lookup
It is happened to other external domain like yahoo.com or gmail.com?

It like that your try to send an email to distribution list at recipietn site. Could you make sure that it is user or distribution? if distribution, please make sure that you ask the recipint IT department to uncheck the "Request all senders are authenticate"

You may try to reinstall the patches at control panel. Reboot the server then send to " same recipient" and verify if message able to deliver.

Hi Friend,

Please check your Send Connector and Receive Connector Rules please try this link for your Problem i too faced the same.



Please clearly read the document and try those it will work on Exchange 2010 also.

Please try and let me known

P. Praveen Raj
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cheto06Author Commented:
removed all udpates with the exception of KB2126440 and still not working.
Have you got any transport rule setup?

Have you also got any email filtering system like Symantec?
cheto06Author Commented:
no, like i said everything was working fine until i applied these updates and rebooted.
cheto06Author Commented:
that is my ISP address. What does it have to do with this?
abdulalikhanConnect With a Mentor Commented:
You need to enter the reverse DNS record for your sending IP against your domain name. Different organizations use different SPAM mechanisms and reverse DNS record is also used to check if the sending domain is a legal domain or not.

This is also known as pointer records.
Also, pls check at mxtoolbox.com for your domain if it is blacklisted. if yes, then you might have to change your sending server ip. Also, make sure that you have a A record with pointer created for the public ip address which is sending out email .. and it shud be created on a public dns server.
It seems that the reverse DNS for your ISP STMP sender is not resolved. Many SMTP hosts don't accept connection where reverse DNS fails.
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