Got this in header of bounced mail. The reply-to address was not *rcn*, but I usually relay outgoing mail through RCN's server because it's typically fast. But it looks like "smtp.rcn.com" (what the heck is "synacor"?) is in some block lists as a source of spam.
Would be nice to get this cleaned up, since I assume there's minimal spam coming from RCN's network.
Diagnostic-Code: smtp; 550-"JunkMail rejected - smtp-fo.rcn.cmh.synacor.com (smtp.rcn.com)
550-[69.168.97.80] is in an RBL, see Blocked - see
550 »
www.spamcop.net/bl.shtml ··· 68.97.80