First, don't put your real information into the e-mail field if you're concerned about that. Second, if you're using identd, set it to use your nick (or something else) as the username instead of using your email as the username.
You cannot hide your host/IP information from mIRC. Some networks allow you to mask that information (the part after the @ in nick!ident@host.com). However, network admins can still see your real details. There are options to hide your true host/IP information through the use of "anonymity" utilities. However, your host/IP really isn't personal and although your ISP could identify who you are if someone gave them your host/IP information, they aren't going to hand that information out to anyone without a court order. So there's little to worry about unless you're doing something you shouldn't.