Once the nameservers change, the records at your current DNS provider stop working. The first step of "Let C Building manage your DNS" brings your current records over, but a few things are yours to check. If nameservers are new to you, start with what nameservers are.
Checklist
- In "Confirm the records to bring over", the email records (MX, SPF, DKIM, DMARC) are checked.
- Records on other subdomains (such as shop or api) and verification records for other services are added.
- DNSSEC is off at the registrar, and the change has taken effect.
- Registrar forwarding features have a replacement.
- Click "Start hosting" in C Building first, then change the nameservers at your registrar within 3 days.
1. Email records
| Record | Where it lives | What it does |
|---|---|---|
| MX | The domain itself (@) | Tells senders which mail server receives your email |
| SPF | A TXT on the domain itself, starting with v=spf1 | Lists the servers allowed to send as you |
| DKIM | A TXT or CNAME at selector._domainkey | Signs your mail so receivers can tell it wasn't altered |
| DMARC | A TXT at _dmarc | Tells receivers what to do when SPF or DKIM fails |
Without MX you stop receiving email. Without SPF, DKIM or DMARC, the email you send is more likely to land in spam or bounce.
Why automatic detection can miss DKIM
DNS has no way to list every name under a domain; each name has to be looked up one at a time. "Detect automatically" looks up common names (www, mail, email verification records and so on). DKIM lives at selector._domainkey.yourdomain, and the selector name is chosen by your email service, so it differs from one service to the next. If the name isn't on the common list, it isn't found.
How to add what's missing
- Use a full import: if your DNS is on Cloudflare, choose "Import from Cloudflare", which reads every record. With other providers, export a zone file (BIND format) and use "Paste a zone file".
- Add it yourself: in the "Confirm the records to bring over" step, click "Add a record", fill in the type, host and value, then click "Add".
- Where to find the values: the record list at your current DNS provider, or the domain settings page in your email service's admin console.
C Building supports A, AAAA, CNAME, MX, TXT, SRV and CAA records. ANAME/ALIAS records and delegated subdomains are not brought over. If you have CAA records, they must allow letsencrypt.org, or your website's HTTPS certificate cannot be issued.
2. Turn off DNSSEC first
When DNSSEC is on, the registry holds a DS record used to check the signatures on DNS answers. After a nameserver change the signatures no longer match, and the domain stops resolving. When C Building detects this, it stops and says: "DNSSEC is turned on for this domain. Turn it off at your registrar first (remove the DS record), wait for it to take effect, then come back. Otherwise the domain would stop resolving."
Turn DNSSEC off at your registrar and wait for it to take effect before you start. Some registrars prompt you during the nameserver change; Squarespace, for example, asks you to confirm disabling DNSSEC (Squarespace Help).
3. Registrar extras
Many registrars' free DNS includes extras such as URL forwarding and email forwarding. These run on the registrar's own nameservers and usually stop once the nameservers point elsewhere. Check whether you still use them and set up a replacement first. What some registrars say happens:
- Squarespace: the domain disconnects from your Squarespace site, Squarespace DNS records stop applying, and PayPal Payment Links stop working (Help).
- Wix: Wix DNS records stop working, Wix can't renew SSL through DNS, and Wix mailboxes need MX records at the new DNS provider (Help).
- Namecheap: host records are not copied to the new nameservers automatically (Help).
4. Order: start hosting, then change the nameservers
After you click "Start hosting", change the nameservers at your registrar within 3 days, or this setup and the records brought over are removed. Don't change the nameservers first and set up afterwards: doing it in that order stops your website and email from working.
Registrar steps: GoDaddy, HiNet, PChome and Net-Chinese, Namecheap, Squarespace and Wix. The full flow is in Let C Building manage your DNS.