Mail from my list server (list.xcski.com, ip 126.96.36.199) to [your customer] is getting bounced with the message:
<[your customer]>: host domain-relay.mspring.net[188.8.131.52] said: 550 Dynamic IPs/open relays blocked. Contact <firstname.lastname@example.org>. (in reply to MAIL FROM command)
And when I try to email the address that it says to contact, I get a further bounce:
<email@example.com>: host madm-corleone.atl.sa.earthlink.net[184.108.40.206] said: 550 Unknown local part openrelay in <firstname.lastname@example.org> (in reply to RCPT TO command)
First of all, I’m not an open relay. Never have been, never will be. And unlike you, when I have an error message say “Contact:”, I make sure the email address actually exists. Can you bozos please fix your open relay check, and fix your bounce messages?