What do you mean by dedictaed IP address? But yes, you do need a fixed IP address.
Are you hosting your server on premise, maybe even on a DS-Lite residential connection? Residential IP ranges are listed at Spamhaus “by default”, regardless of whether they are ipv4 or ipv6 addresses.
If you want to host an email server on premise, you need at least a business subscription, with at least one fixed IPv4 address that does not reside in a residential range. And If you want to use IPv4 and IPv6, you need proper Dual Stack. However with most ISPs these subscriptions are expensive. The cheap business subscriptions are often the same as home user subscriptions, with maybe a faster hotline, and even if you can get a fixed IP addresses with such a subscription, these addresses could be in the same range as the dynamic home user IPs and therfore it’s very likely, that they are also listed at Spamhhaus, at least in a PBL list.
No, because nobody who operates a productive mail server would run it on IPv6 only.
Ooops… Why does a three year old post suddenly appear here. Anyway, maybe the answer will help someone else, I assume OP has solved his issue in the meantime