Well besides US law, it's against Charter TOS, which I think is his problem. I would guesst either his IP is black listed, or the IP of the mail servers he is sending to is blocked.
From Charter TOS6. NO “SPAMMING"
Customer will not use, or allow others to use, the Service to send unsolicited messages or materials, bulk e-mail, or other forms of solicitation (“spamming”). Charter reserves the right, in Charter’s sole discretion, to determine whether such posting or transmission constitutes unsolicited messages or materials. Forging, altering, or removing electronic mail headers is prohibited. Deceiving any recipient as to the identity of the sender through any process is prohibited. Customer may not, or allow others to, reference Charter or the Charter network in any email in an attempt to mislead the recipient.
**Edit**
Just thought I would also say this isn't anything personal. You sound like a nice enough guy, and you were trying to lend a hand else where on the forum and I like that. Maybe I can help you set up a legitimate and solicited email system? Maybe put together a website listing all the local events, including yours. And then on the page have a "Subscribe to my mailing list button". Assuming your running your own mail server, I can show you how to load balance, set up mx records, adjust your PTR, and all that fun stuff. As long as your mailing list is going to subscribers only, and you have a working, easy to use unsubscribe ability, it isn't spamm. Join the light side Mr Darth Vader. :-)