Maybe it is just because it is a new domain? I’ve just read the following:
Domain reputation
- Reputations are built over time, and building a good reputation takes longer than building a bad reputation.
- Experience has shown that an unknown reputation has a much higher risk of emitting spam than known-good domains, so unknown reputations begin as “poor” by default.
- Anonymity does not contribute to a good reputation.
- Domain and IP reputations affect each other.
- If domains are used in legitimate traffic for enough time to establish a good reputation, DBL will notice that and remove the listing.
- DBL will also notice if domains are used for activities that cause poor reputations, such as spam or other “blackhat” pursuits.
I’ve bolded the two parts which if I understand correctly indicate that if I continue to send legitimate email my domain’s reputation should increase (slowly) and once over a threshold will trigger removal from the blacklist.