Thanks a lot for reaching out. To prevent account details being shared in the public domain, feel free to send me a PM with what you're wanting to set your rDNS to and I'll get a task raised on our end.
Please confirm what you want the rDNS changed to; there are 3 options available:
1 - username.plus.com – This is the default setting.
2 - IP.plus.com - 1-1-1-1.plus.com as an example.
3 - anything.domain.com - e.g. mail.bbc.co.uk – To use this option you will need to configure the forward record on the domain. We are required to prove you own the domain before any changes can be made and this will serve as verification. The domain can be hosted on the account or externally.
Please confirm which of the above you would like to be configured.