“The old domain was burned– so we started fresh.” A phrase that is often heard in practice.

A supposedly quick fix, but one that usually leads to even greater delivery problems in practice.

The idea of starting afresh with a new domain and achieving better results sounds tempting. However, today’s mailbox providers (MBPs) and spam filters have long since seen through such manoeuvres. Simply using a new domain without building a stable positive reputation – and, above all, without improving sending behaviour and quality – usually only makes the situation worse.

A positive IP reputation alone is no longer enough to reliably reach the inbox. Domain reputation has become another crucial factor. Continuous monitoring of relevant metrics is also important.

IP reputation: the proven technical foundation

IP reputation forms the basis for successful delivery. It stands for technical integrity:

Stable and secure infrastructure and clean authentication prevent abuse. A well-thought-out IP warm-up, correct configuration and authentication are prerequisites for emails to be accepted at all.

However, the IP alone is no longer granular enough to clearly distinguish good from bad actors. This is where the domain and its reputation come into play.

Domain reputation: identity and trust

Mailbox providers no longer evaluate only IPs, but a variety of factors and elements relating to the sender and the email, including the sending domain. This can be clearly assigned to a company or a specific mail stream – and is therefore an additional, very precise quality signal.

Especially when using shared IPs, the domain acts as a decisive differentiating factor and enables a precise evaluation of the sending quality – regardless of the shared IP infrastructure.

In short:

IP = technical basis for secure delivery
Domain = identity and long-term source of trust with a decisive impact on deliverability

Only when both levels have a positive reputation can a stable reputation profile be created.

Domain warm-up is mandatory

The same applies to a new domain as to a new IP: trust must be established first. To protect their users, MBPs monitors various signals, such as volume, engagement, authentication, complaints and bounces.

Starting with high volumes immediately triggers security mechanisms. The possible and realistic consequences include delayed delivery, increased filtering or even rejection of the email.

Reputation building begins before the first mailing.

Clean technical configuration and strategic warm-up preparation are crucial:

Set up DNS entries correctly

DNS entries are central technical elements for email delivery. They ensure that domains and IP addresses are resolved correctly and that the necessary information is available for MBP to query.

Configure authentication cleanly

SPF, DKIM and DMARC must be implemented completely and without errors. These standards confirm the legitimacy of the sender and are considered central trust signals for MBPs.

Select subdomains carefully

Using separate subdomains for different types of mailings – such as transactional and marketing emails – creates transparency, enables separate reputation assessment and reduces risks in the event of problems in one mailing channel.

Gradual volume build-up

Small, active recipient groups at the beginning and a gradual increase in volume form the basis. Flexibility is crucial – speed and scope may need to be adjusted.

Continuous monitoring

Continuous monitoring of email performance data and authentication errors enables early detection and correction of anomalies. This allows problems to be identified quickly and countermeasures to be taken in a targeted manner.

Domain age also counts! A domain registered for a longer period – even without previous email use – appears more trustworthy than a new registration. An existing web presence is even better. A domain created shortly before the start of a campaign quickly arouses suspicion – no matter how reputable the sender is.

Further details and practical tips on this topic can also be found in the webinar recap on IP and domain warm-up.

Changing domains as a solution to the problem?

The reflex to switch to a new domain when problems arise is understandable – but usually counterproductive if the true causes have not been identified and remedied. MBPs consider such changes to be behavioural anomalies: new domain but same content, same sending behaviour, same recipients = very suspicious evasive manoeuvre.

The result is exacerbated delivery problems, and without a change in sending practices, the problems will persist. MBPs recognise recurring patterns and evaluate them increasingly harshly. The sustainable approach, on the other hand, is to improve the quality of your mailings – through list maintenance, positive engagement and the consistent application of best practices.

Domain warm-up even when changing ESPs

In addition to new IPs, a platform change may also require a new sending domain. Often, a new subdomain is set up or a different domain is used for sending via the new ESP.

This means

• The new (sub)domain must build its own reputation – even if the brand is already established.
• New IPs, different signature paths and changed headers alter the overall image of the sender in the eyes of the MBP.

Even if an existing domain continues to be used, the new technical conditions influence the reputation and trust must be rebuilt.

Therefore, when changing ESPs, the following applies:

• Build IPs and domains according to uniform warm-up principles.
• Continuously monitor email KPIs.
• Plan the warm-up phase well and do not rush anything, even if there is time pressure.

This allows trust to be built up systematically on the new platform.

Monitoring: no control without data

You can manage reputation only when you make it visible and measurable. MBPs do not provide complete insights, but monitoring systems show trends: complaint rates, authentication errors, spam trap hits, bounce rates, or engagement rates.

Those who have access to reliable data sources and analyse this data regularly can identify problems early on and react in good time.

The Certified Senders Alliance helps senders make trust measurable – through transparent insights into real email performance data. Certified senders benefit from a stronger relationship of trust with mailbox providers and a commitment to quality in optimised delivery and reduced filtering.

Conclusion: Begin correctly rather than repairing later.

Those who consistently maintain both IP and domain reputation create sustainable sending quality – the basis for long-term reliable deliverability.

Well-prepared sending on new infrastructure builds trust – restoring a damaged reputation, on the other hand, is very time-consuming and costly.