Would settings up Sendmail cause infinite loops with my ISP's server?

[Ace69]

I WAS thinking about setting up a Sendmail mail server on my Linux server at home. I work at my ISP and I asked one of the network engineers if it would be OK if I set one up for myself and had a few mailboxes on it. He said no, because it would cause loops with their Sendmail server and take it down. Is this true? I really wanted to set one up at home so that I could learn about it more, but I guess if it is going to screw things up with them, then I guess I have no choice.

Any ideas on why it would do this and any way that I could set one up with no problems?

Thanks alot.