Celso writes, "Can you please help me verify that my IP addresses are not on any blacklist?"
No, I cannot, Celso. And here's why: You're going to be on somebody's blacklist somewhere. The IP address you use, the domain you use, they could be on anybody's blacklist anywhere. Even if you're not a spammer. Some blacklist maintainer could be mad at your ISP or their upstream provider, or they could be trying to list anybody who is associated with some company because they don't like that company.
Forget that. Whether or not you're blacklisted, that is the wrong question to ask.
What you need to ask yourself is: Where is your mail being blocked?
When you look at bounces, what are you seeing?
Are you seeing bounces that refer to a specific blacklist issue?
Are you seeing LOTS of bounces referring to some well-known blacklist?
If you're not answering "yes" to one of the questions above, then I wouldn't worry about it.
If the IP address you use to send mail is on Spamcop, Spamhaus, or UCEPROTECT, then you might have a problem. Being on any of those blacklists tends to indicate a real spam problem, and suggests you need to figure out what's going wrong, and you need to fix it.
But, there are a lot of blacklist lookup tools online that include tons of other blacklists-- including a number of blacklists that aren't widely used to filter mail. In short, they don't matter. Or the lookup site include blacklists that are long since dead. Or they do other things that don't exactly fill people with confidence. What really matters is what impact a blacklisting has on your ability to send mail. Being on "the blacklists" themselves is not the real problem.
As always, if you have a spam problem, you need to address it. Spam is bad. Stay away from spam, and you'll stay away from the blacklisting issues that can cause real trouble. And keep in mind, being listed on some tiny little blacklist you've never heard of does not mean you're ever going to see an email get bounced as a result. Look at APEWS -- well known ISP administrators openly refer to it as a joke, and nobody uses it to filter spam. Is an APEWS listing a problem? In short, no.
It all boils down to this: Not all blacklistings matter. Keep your nose clean (don't allow or send spam), watch your bounces for blacklist references (meaning you're on a blacklist that actually has an impact), watch for and deal with spam complaints properly, and you'll be just fine.