Exchange 2010 Event ID "Transfer" delayed and fail delivery

I have a user who received a "Delivery is delay to these recipients or groups:"
I ran get-messagetrackinglog cmdlets and traced the message and noticed the Event ID "Receive" with source "Store..." then Event "Transfer" Source "Routing" for the message.

Can someone explain better than MS what I am seeing here? Is the failure on our side or is what?

Also, checked the Queue Viewer and it is there with 400 40407 message Delayed. Nothing else in queue.

Thanks yet again, in advance

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Nathan PSystems ArchitectCommented:
400 4.4.7 is the error code when Exchange tried to deliver your mail.

It could be too many reasons for it to be resolved here without seeing some of the logs.

It could be:  
TLS issues (you or the other side expects TLS encrypted delivery and the other side doesn't)
The remote server (you are trying to send to) is down/unavailable
The remove server is greylisting you, causing you to retry (a known anti-spam technique, as spammers won't bother retrying, they'd rather move on)

Try sending mail from command line on your mail server to one of these servers to see what will be the response from the remote server.  It might help.

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kryanCAuthor Commented:
Thanks that took me right into a DNS issue when looking at their anti-spam policy. That lead me to my MX then to ISP and found out Reverse DNS was never updated when we applied a new firewall and new IPs for email servers.

Thanks for putting me on the right track!
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