microsoft exchange 2010 , Outlook 2007

pramod1 used Ask the Experts™
a user is trying to send e-mail and getting following error

A temporary error occured while delivering to the following address(es):

  <>: 451 Timeout trying to connect to MX servers for domain

I will continue trying to send the message until it is delivered or expires.

can you explain why he is getting such error
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the server is telling you that it cannot connect to the recipients mail server, as listed in their public internet records (MX records)

Your server is getting the wrong MX records
The recipients MX records are incorrect.
Your server cannot connect to the recipients server

I'm afraid you'll have to do a biut of digging to find out which one, but if you can e-mail other people it seems unlikely to be an issue at your end unless you are on a blacklist.
The issue is on the other domain's side.  There are many potential causes, but if you can email anyone else it is very slim the issue is on your side.

A reverse on the IP listed in their MX record does lead to one possible problem on your side, but it really is their problem.  Their reverse IP does not match in external DNS.  If reverse IP addresses don't match then many anti-spam products cause SMTP to fail.

C:\Windows\system32>ping -a

Pinging [] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

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