Please be informed that the domain (my.xxx.com) is resolving to following IP's.
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telnet 174.132.149.251 25
Trying 174.132.149.251...
Connected to fb.95.84ae.static.theplanet.com (174.132.149.251).
Escape character is '^]'.
220-sunbird.websitewelcome.com ESMTP Exim 4.69 #1 Mon, 10 Oct 2011 05:29:20 -0500
220-We do not authorize the use of this system to transport unsolicited,
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Could you please go ahead and contact where you have configured WHMCS and get back to us if you need any further assistance.