Networking and reverse DNS
Find your server's IP addresses and gateway, set reverse DNS so mail is deliverable, and change the DNS resolvers it uses.
Manage your cloud server's network configuration. Applies to all VPS and dedicated servers.
Primary network
The details your server's own configuration must match:
| Field | What it is |
|---|---|
| Interface | The network device name, e.g. ens3 |
| MAC | The interface's hardware address |
| Type | Public or private |
| Speed | Inbound and outbound limits |
IPv4 addresses
Each address is listed with its gateway, netmask and resolvers. You need all three if you ever configure networking by hand — after a manual OS installation, for instance.
Reverse DNS
Reverse DNS maps your IP address back to a hostname. Select Reverse DNS beside the address to set it.
Set this before sending any email. Most receiving mail servers reject or heavily penalise mail from an IP with no reverse DNS, or whose reverse DNS does not match the sending hostname. It is the single most common reason mail from a new VPS goes nowhere.
Set it to the server's fully qualified hostname — mail.example.com — and make
sure a matching forward A record exists pointing back to the same IP. The two
must agree.
DNS resolvers
Your server needs two resolvers to look up domain names. The system defaults are
Cloudflare's 1.1.1.1 and 1.0.0.1.
Change them under IPv4 Public DNS Resolvers if you have a reason to — a filtering resolver, or your own internal DNS. Otherwise leave them.
Changing resolvers here sets what a rebuilt server receives. On a running
server, also update /etc/resolv.conf or your network configuration, or it
keeps using the old values.
Check it worked
Reverse DNS, from any machine:
dig +short -x 203.0.113.10It should return your hostname. Propagation can take a few hours.
Forward and reverse agreement:
dig +short mail.example.comThat should return the same IP you just looked up.