[bitfolk] IPv6 reverse DNS question

Hi folks I'm running mail-in-a-box on a Bitfolk VPS. https://mailinabox.email/ It's making the following complaint: "This box's reverse DNS is currently aquitaine.richardskingdom.net (IPv4) and 2001-ba8-1f1-f037-0-0-0-2.autov6rev.bitfolk.space (IPv6), but it should be aquitaine.richardskingdom.net. Your ISP or cloud provider will have instructions on setting up reverse DNS for this box." This is with reverse DNS set to "automatic" in the Bitfolk panel. The only other panel option seems to be to delegate the reverse IPv6 zones to my name server. I'm using the mail-in-a-box built-in name server, however, and delegating to that produces the following result: "This box's reverse DNS is currently aquitaine.richardskingdom.net (IPv4) and [Not Set] (IPv6), but it should be aquitaine.richardskingdom.net ..." I infer that mail-in-a-box name server is not setting reverse IPv6 records for itself. There doesn't appear to be a way to tell mail-in-a-box to set the reverse DNS correctly via its GUI - there is no option to add a custom PTR record (other record types can be added). I don't know what name server software is running under the hood, and I'm loath to make config changes except via the GUI in case they get overwritten when mail-in-a-box updates. Can anyone advise me how to set my IPv6 reverse DNS to aquitaine.richardskingdom.net? I should note the mail server works (I am sending this message through it) so this is only to make the error message go away (and possibly to get IPv6 mail transportation working correctly). If this sounds like an ignorant / nonsense request, congratulations, you have detected successfully that I have no idea what I'm doing with IPv6... Thanks in advance Richard.