I have my Synology Diskstation updating my Dyno custom domain just fine currently. The issue is I would like to only update a single alias in the custom domain. As it stands right now, if I put alias.customdomain.com my authentication fails. If I put customdomain.com only it updates only the top level address. If I put just a group name it authenticates, but also only updates the top level domain.

Does anyone have a solution to this?