Kennth, I looked at your ISP's DNS and it appears that it is correct. They do have an SMTP server at mailhost.cin.net/204.120.48.3. If I were testing things I'd use the IP #'s (204.120.48.3) not the alpha (mailhost.cin.net). That can reduce any DNS problems. (DNS can get terribly complicated when you get multiple domains and Class C's all in one pile-which is your ISP problem not your's)
I think you're doing great. We all have these problems and questions when we first start. Dealing with ISP's is always difficult because it easy for them to say its your problem. I think Rusty's advice will solve your problem!
