Before you start, make sure you have access to your domain's DNS settings — you'll need to add records there. If your domain is registered with Namecheap, GoDaddy, Cloudflare, or similar, log into that account and find the DNS management section.
Starting the setup
Go to Domains and click Add Domain.
You'll be asked to choose between adding a root domain or a subdomain:
Add New Domain — for a root domain like yourdomain.com. This requires four DNS records: MX, SPF, DKIM, and DMARC.
Add Subdomain — for a subdomain under a domain you've already verified, like mail.yourdomain.com. This only needs an MX record since the other records are inherited from the parent domain.
Entering the domain
If you're adding a root domain, type it in without www — just yourdomain.com. The system strips https://, www., and any trailing paths automatically, so you don't have to be precise.
Click Continue and the domain is registered to your account. You'll be taken straight to the DNS setup page where you'll see the exact records to add.
What happens next
The domain won't be active yet — it sits in Setup Required status until you add the DNS records and verify them. See DNS verification for the next step.
You can come back to the setup page any time by going to Domains and clicking Continue Setup on the pending domain.