Messages aren't being delivered to a specific remote domain.

	The route domain path is incorrect, which produces a "Host unreachable" error.
	Check the path on the Domain Properties property sheet for the remote domain.

	The receiving server is down or the message cannot be delivered for a variety of reasons.
	Check the .rtr files in the Queue directory to determine the cause. Check the retry counters in Performance Monitor. Check the receiving server.

	The name is incorrect or the address is invalid.
	Check the name and path.

	Transport Layer Security (TLS) is required for connections. The key certificate is invalid or the encryption levels don't match.
	See if the use of TLS has been overridden for the remote domain in the Domain Properties property sheet. Check the TLS encryption level on the Directory Security property sheet. Make sure it matches the level required by the receiving server. Use the Key Manager to set up key pairs.

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