Keep your home server reachable with Dynamic DNS

Fastmail has introduced Dynamic DNS for customers who host their domain’s DNS there, helping home-hosted services remain reachable when a residential internet connection’s IP address changes. A Dynamic DNS client or router updates a hostname to reflect the current address, using the long-established dyndns2 protocol. To enable it, users create a dedicated Dynamic DNS API token, then add a Dynamic DNS record for the desired hostname in their domain’s DNS settings. The record begins empty and can be updated through the API.

The feature includes a dyndns2 endpoint compatible with clients such as ddclient, plus a simpler URL-based endpoint suited to scheduled curl commands. Updates can use the request’s IP address or specify an IPv4 or IPv6 address; HTTP status codes report success or errors. Security is designed to limit the damage a stored token could cause: it can change only explicitly created Dynamic DNS records, not ordinary A or AAAA records, mail-routing records, or DKIM keys. Fastmail recommends sending credentials over HTTPS and protecting client configuration files that contain tokens. The addition also addresses a practical reason some customers could not host their DNS with Fastmail, allowing them to keep home services accessible while managing their domain’s email-related DNS in one place.