You're posting a connection issue under 'mirc help', when there's a whole section about connection issues right next to it, and there's stickies near the top of that where people have had the same kind of problems.
This is not an 'mirc' problem, you would've gotten this message regardless of the program you use. You didn't say if you'd read the link you pasted.
Either you're infected with something that you need to get rid of, or your ISP lets lots of people share the same IP address, or you've been assigned an IP formerly used by someone infected, or there's been so many problems with your ISP that Dalnet just range-banned a big section of your ISP.
If your ISP changes your IP address each time you connect, it would be difficult to fix this problem since any effort you make would just be clearing that address for the next person.
I don't know about Dalnet, but in the past there have been irc networks which send these kind of messages containing an email address which nobody ever checks.
