However, I was not aware of the possibility that an IP address has been used in a DHCP role in addition to static own. Is there a way to check this? That could support my complaint with the ISP.
M$ (and others) block entire IP ranges. As JP has said, your IP will lie in a 'residential' block of IP addresses. Trying to get an individual one unblocked will probably be more trouble than it is worth if it is even possible. Gmail is likely to block you at some stage as well, and possibly others. You will be firefighting the whole time.
It is unlikely your ISP can, or will, do anything about it, and they may well tell you that hosting a mail server on their IP addresses is not in their terms. I doubt they will be sympathetic to your case.
You may also have difficult setting up rDNS.
So yes, you may be able to get it delisted as per Garys comments, but you are likely to run into an endless list of niggles,
A few big players are now monopolising the market and are determining who can host mail - and are pushing you very hard to use their (paid for) services. Not to mention mail filtering services like Mimecast etc.
I would save my time and effort and either move to a different IP/host that is not so easily blocked - either a proper business host with genuine static IP (hard to check), some sort of cloud VM, or get yourself an upstream relay like authsmtp or smtp2go and let them deal with the problem.
I know none of this is what you want to hear, but you are asking us for our knowledge and experience, and regrettably from experience these are the answers.