Have clients who have contacted me to say their emails sent to other people, are bouncing back to them, with the message that they have been detected as junkmail by RBLs
Done a check at MXTOOLBOX, and yes telecoms IPs are listed on a lot of RBLs
http://mxtoolbox.com/SuperTool.aspx?action=blacklist%3a210.54.141.251&run=toolpage