The situation
To use an external domain with Maildoso, you connect it in your dashboard and we give you 2 nameservers per domain to add at your registrar. That points the domain to us so we can manage its DNS.
Cloudflare Registrar is a special case. Domains registered through Cloudflare Registrar are locked to Cloudflare's own nameservers and cannot be pointed to another provider's nameservers. Because our setup requires our 2 nameservers, such domains cannot be connected as-is.
What you can do
Transfer the domain to a registrar that allows custom nameservers, then connect it and add our 2 nameservers.
Use a domain registered elsewhere. A domain that only uses Cloudflare for DNS but is registered at another registrar is fine — the limitation applies specifically to domains registered at Cloudflare Registrar.
Register the domain through Maildoso instead.
Ask us to review your case. Open a chat with the domain names and we'll confirm the exact next step.
Good to know
Until a domain is fully connected, please hold off on creating mailboxes on it so you don't run into setup issues mid-way. We're happy to confirm when a domain is ready.