Blacklisted - is that my problem?
Following @ JoshData’s post What validation tools do you use? I checked my box’s IP address with mxtoolbox.
The IP is listed UCEPROTECT-Level3 which means the entire subnet is flagged.
But on DigitalOcean community I see this: “Mail providers should not check against UCEPROTECT’s blacklist database and even if the IP address is listed there you should not have any issues with the mail delivery.”
Now I can’t tell if there’s something wrong with my setup or if the problem lies elsewhere 
All and any help here will be very much appreciated! 