The CBL is intended to be used only on inbound email from the Internet.
If you are being blocked from IRC, Chat, web sites, web email interfaces (eg: you're using Internet Explorer, Firefox, Chrome, Opera etc to send email) or anything other than basic email with a mail reader like Exchange, Thunderbird etc, the provider of this service is using the CBL in an unsupported way.
Many administrators have discovered that the CBL is also highly useful in protecting other services such as IRC or web sites, often as an anti-fraud mechanisms etc. After all, an infected computer spewing malware can also be utilized to perpetrate other abuse of the Internet, including outright criminal activities such as DDOS and computer breakins.
Strictly speaking, use of the CBL for non-email purposes is a violation of our Terms of Service, however, we do not wish to prevent administrators doing what they feel is necessary to do, nor could we in any practical sense.
If you are being blocked from services other than email, you should contact the service itself on how to resolve the issue.
If you are an end user: If you get an immediate popup indicating your email was blocked when you attempt to send email, this means one of two things:
If you get the blocking email message by return email (instead of by immediate popup), your provider is probably listed in the CBL, not you. Contact your provider and tell them that their IP address is listed by the CBL.
Note that the CBL is not responsible for how providers misuse the CBL. This is their problem, not ours.
If your IP address changes periodically (such as with reconnecting to your provider, connecting through an Internet Cafe etc), this is usually a dynamic (DHCP) IP address, meaning that it's most likely not you that is infected. As above, make sure that your mail reader is configured correctly as per your provider. In this case, delisting the IP address will probably not do anything useful.