Domain age checker for cold email

The two numbers are ReplyLead's operating rule for every campaign it launches, not a threshold Google or Microsoft publishes. ReplyLead's infrastructure guide says it plainly: we do not claim that a provider automatically trusts a domain because of its registration date.

The rule is caution about first impressions. A domain registered last week and a mailbox with no sending history give receivers nothing to judge, and the first emails a prospect sees from a new domain should not also be its first emails ever. Google's sender guidelines tell bulk senders to increase sending volume slowly to avoid delivery problems; the age gate and the warmup are where ReplyLead's slow start begins.

The warmup floor is 14 days. ReplyLead's warmup guide plans a ramp of 2 to 2.5 weeks, and the checker lets you set 18 or 21 days if your own plan is longer. Buying the sending domains early is the cheapest fix: a domain bought a month before the campaign is ready by the time its mailboxes are.

ReplyLead read the registry registration date of 186 of its sending domains and compared counted replies by age. Domains registered 10 or more years earlier showed 4.41% unique replies per contacted lead; younger domains showed 3.19%. Only four of the older domains had sends, and audiences, programmes and mailbox providers were not matched, so the aged-domain benchmark reports an association, not an effect of age.

Age is also not ownership. When someone buys an aged domain, the registry keeps the original registration date, and nothing in that date shows who sent what before. That is why the checker notes a move to a new registrar in the last 90 days, and why ReplyLead warms a bought domain's mailboxes like any other.

RDAP is the Registration Data Access Protocol. ICANN describes it as the replacement for the WHOIS protocol, and RFC 9083 defines how a registry reports a domain in JSON, including a registration event (the object instance was initially registered) and a transfer event (moved from one registrar to another). RFC 9224 defines how a client finds the registry server for a name through IANA's bootstrap file.

The checker follows that path. It reads the bootstrap file, asks each domain's registry for its record, at most 4 at a time, and waits up to 10 seconds for each answer. The questions go from your browser to the registries; ReplyLead's servers never see the list.

Some registries publish no RDAP service a browser can read. On 3 November 2026, IANA's bootstrap file listed RDAP servers for 1,203 top-level domains, with none for .co, .us or .me. For those names the checker says Unproven rather than guess; the creation date is in your registrar account or the registry's WHOIS.

To plan new domains rather than check existing ones, the cold email domain generator suggests names and checks through RDAP whether each one is still unregistered.

The rule is the one ReplyLead applies before any campaign starts: the registry registration date plus 30 days, and the warmup start plus its length, whichever is later. Dates are counted in whole UTC days. A domain registered at 11 PM counts that day as day one, so the 30th day can arrive a few hours earlier or later than in your time zone.

The same script draws the example on this page, the figure and every result you check, and its tests run against real answers saved from the .com, .org, .io, .xyz and .app registries.

The checker cannot see your mailboxes. The warmup date is what you enter, and Not started assumes the warmup begins today. It also cannot see reputation: it does not read DNS records, test inbox placement or predict replies. The deliverability checker reads SPF, DKIM and DMARC, and the mail provider lookup shows who hosts a domain's mail.

Analytics records only counts, such as how many domains were checked and how many can send. The CSV download is built in your browser.