something strange in message queues log

	To	From	Date	Route	Size	Last Error	Next Attempts
	xxx@mydomain.com	pipinge30@raveisre.com	Wednesday, Mar 19, 2014 09:44:03 PM HKT	[192.168.100.19]:41025	14920	421 4.4.0 [internal] Failed to connect: no mail servers for this domain could be reached at this time	Thursday, Mar 20, 2014 05:29:04 PM HKT	8

My comany just bought a new SMG with version 10.5.1-2.

SMG was configured but something strange in message queues log shown above.

mails sent from pipinge30@raveisre.com to several internal recipients (some recipients' addresses aren't available) were routed to the IP address 192.168.100.19 which isn't in the range of my internal network. My internal sub-network is 192.168.1.0/24.

These mails may be considered as spam mails, but why does SMG try to route these mails to that IP address? Is there any configuration wrong in SMG?

Any information, help would be appreciated!