Compare sender reputations during a domain merger

When an Australian organisation absorbs another company, the merger can leave two domains sending similar messages to the same customers. This guide explains how to use the platform to compare the sender reputation of two domains in a merger, identify the safer sending identity and reduce the risk of legitimate mail being treated as spam.

Sender reputation reflects how email providers and security systems perceive previous mail from a domain. Authentication records add another layer by showing whether a message was authorised to use that domain, but passing SPF, DKIM or DMARC does not guarantee that a sender has a good history.

A reliable comparison therefore needs consistent tests, a record of the observed results and an understanding of each organisation’s mail infrastructure. The platform supports this process through domain reputation checks, authentication tools, bulk checking and an API for integrating trust verification into merger workflows.

Define the two-domain comparison

Start by identifying the proposed surviving domain and the legacy domain, then list the systems that send email for each. Include transactional services, marketing platforms, customer support tools, shared sending subdomains and any contracted providers. A strong result for the main domain may conceal weaker infrastructure elsewhere.

The free sender trust checks provided by Trusted Sender Score offer a consistent starting point. Record the result for each root domain and major sending subdomain at the same time. Many Australian businesses use .com.au, while .au is becoming more visible, so comparing domains with different endings can still be useful when both belong to the merged organisation.

Build a reproducible baseline

Run the reputation check close together, preferably during a normal Australian business week, and keep a dated record of the outcome. Include relevant observations such as blacklist visibility, authentication posture and whether the result changes after checking again. A single observation should be treated as a snapshot rather than proof of permanent sender quality.

Compare technical footprint as well as the headline result. A newly registered corporate domain may have little sending history, while an older domain with irregular traffic may still possess useful reputation. Check whether both organisations send from the same Australian internet service providers, email platforms or overseas mail gateways, as shared infrastructure can affect how recipients recognise their messages.

Compare authentication, not just reputation

SPF identifies authorised sending servers, DKIM signs messages and DMARC aligns the visible sender with those controls. Compare the presence, validity and coverage of all three records for both domains, then identify missing services or unsigned subdomains. Pay particular attention to alignment: a valid DKIM signature may have little value if it does not match the domain shown in the From address.

The platform’s SPF, DKIM and DMARC resources can be used with the detailed authentication checklist. Avoid changing production DNS records merely to improve a score. Authentication changes should form part of a coordinated migration plan, especially if Sydney and Melbourne IT teams support the two organisations separately.

Plan the domain transition

Decide which domain will appear in the From address, which will handle replies and which will retain SPF, DKIM and DMARC records. Update the surviving domain’s authorisation lists to cover every legitimate platform, while removing obsolete providers only after traffic has ceased. Marketing teams should also update signatures, footer addresses, support links and authentication instructions.

Use a staged rollout rather than switching all traffic on one day. Lower relevant DNS time-to-live values in advance, test transactional and campaign mail, and monitor results across Australian business hours. Sydney operations may begin sending while Melbourne teams are still handling morning workloads, so regional scheduling can prevent a temporary volume spike from creating a poor first impression.

Automate repeat checks

For a merger involving many related domains or sending subdomains, bulk domain checking can establish a shared baseline without repeating each lookup manually. Group results by legal entity, brand and sending platform so that teams can distinguish expected exceptions from controls that require remediation. Repeat the batch at agreed intervals to track changes after DNS and mail-routing updates.

The API can also send trust results into internal dashboards, ticketing systems or merger workstreams. Define which fields to collect, how long to retain them and who receives alerts when authentication breaks. Cached results and sensible request intervals help prevent duplicate scans from creating unnecessary traffic, while access credentials for the API should be stored using normal organisational security controls.

Protect privacy and legal obligations

Merger planning often involves transferring customer records, consent histories and responsibilities between entities. Where the Privacy Act 1988 and the Australian Privacy Principles apply, document who controls the sending data and who authorised its use. The Office of Australian Information Commissioner provides guidance relevant to Australian organisations, particularly when customer lists or support correspondence are integrated during the transition.

Before publishing screenshots or using platform findings in customer-facing material, read the legal notices and follow any permitted-use, attribution or data-handling conditions. Keep internal reputation reports separate from marketing claims unless the evidence can be explained clearly. This avoids turning a technical comparison into an unsupported public statement about one organisation’s security.

Monitor the merged sending estate

After the cutover, track authentication failures, spam complaints, delivery to Australian inboxes and customer support reports. Compare both domains rather than assuming the new identity inherited the old domain’s trust. Marketing campaigns should also be checked for misleading forwarding paths, broken links and unfamiliar display names, which can make legitimate merger communications appear suspicious.

Set explicit thresholds for proceeding, pausing or reversing the migration. If the newer domain develops poor results while the legacy domain remains trusted, retain the established sending route until improvement is demonstrated. Australian customers can report deceptive messages through the Australian Signals Directorate’s Scamwatch service, so suspicious patterns should also prompt internal investigation. The primary sending identity should change only when reputation, aligned authentication and sustained delivery evidence all support the transition.