The error message tells you why, if you only knew what Z-Lined meant (google it), DNSBL meant (google it) or used the link provided to check your IP address.
Short story, the IP address you were using is on a spam list that's being checked. Doesn't mean it was your fault, but that's what is happening regardless.
If your ISP assigns dynamic addresses, you'll probably get another one assigned soon enough. Especially if you turn off your modem for a while.