Over the past year, we have spoken a lot as an industry about disruption, rising passenger expectations and the role communication plays in protecting trust. When operations are under pressure, we know passengers look for clarity. They expect updates that are timely, accurate and clearly coming from their airline. In those moments, communication is not a secondary function. It defines the experience.

But there is one foundational issue undermining that experience for passengers and that is invalid email addresses.

When we discuss email performance, the focus often sits on infrastructure, authentication protocols or sender reputation. In our industry, where email is primarily operational rather than marketing-led, the impact of poor data quality is underestimated.

It should not be.

Damian Carter, Technical Operations Manager at 15below, shares his insights on how airlines can prevent email delivery failures, maintain inbox placement, and keep passengers informed during disruption through better data validation. Damian manages the technical, backend, and operational aspects of the 15below platform and brings over 25 years of experience in infrastructure, with a focus on security and email deliverability.

The operational risk of invalid email addresses

Every time an email is sent to an address that does not exist or is badly formatted it generates a hard bounce. Email service providers monitor bounce rates closely. When those rates exceed accepted thresholds, sending behaviour can be throttled or blocked all together.

We regularly see Yahoo enforcing throttling on our email delivery rates and can see this occurs following delivery attempts to bad or inactive mailboxes. This throttling can mean a delay of two hours or even more if we attempt to deliver to another bad or inactive mailbox. Yahoo close inactive mailboxes after 12 months and use these as spam traps to intentionally identify senders who are not validating email addresses or maintaining list hygiene.

Unlike marketing programmes, operational messaging does not rely on subscriber lists that can be routinely cleaned or suppressed. If an invalid address is captured during a booking, it may continue to receive repeated send attempts such as confirmations, reminders and disruption updates.

The result is increased bounce rates, reputational damage with mailbox providers and reduced inbox placement, not to mention delayed email delivery for valid passengers.

Poor data hygiene does not just affect individual emails. It can affect your entire sending reputation.

For a broader look at email deliverability and performance, whilst adhering to changing industry requirements, see our blog on getting email deliverability right, where I share my insights alongside Marcus Dibb, our Digital Interaction Designer.

The passenger and brand impact

When operational emails fail to reach the inbox or are delayed, the consequences are immediate.

Passengers will miss confirmations, schedule changes and disruption updates. They are then forced to seek answers elsewhere, through search engines, third-party apps or social media, where information may be inconsistent or incomplete. 

Industry research from the UK Civil Aviation Authority shows that when disruption communications are delayed, incomplete, or inconsistent, passengers often turn to third-party sources for information, increasing uncertainty and risk of miscommunication.

In those moments, the airline loses control of the narrative and its position as the single source of truth.

Clear, proactive communication reduces uncertainty, lowers contact centre demand and improves service recovery. It directly influences CSAT, NPS and long-term loyalty. But that only happens if the message is delivered, and within relevant timescales.

28% of passengers say that poor customer service during disruption makes them less inclined to fly with the same airline in the future, highlighting the impact of operational communication on long‑term loyalty.

We often talk about turning disruption into an opportunity to strengthen trust. That opportunity disappears if the communication fails at the first hurdle.

You can read more of my thoughts about how airlines can master operational email deliverability in our post Mastering Operational Email Deliverability for Airlines and Travel Companies.

Why validation at source matters

The most effective way to prevent this issue is validation at the point of data entry. Whether captured via booking flows, mobile apps or agent-assisted channels, email addresses should be checked in real time to prevent invalid or mistyped data entering the system.

This approach:

• Reduces hard bounce rates.
• Protects sender reputation.
• Improves inbox placement.
• Ensures operational messages reach passengers when needed.
• Reduces avoidable contact centre pressure.
• It is a small intervention with significant impact.

Whilst there are dedicated services to validate email addresses in real-time using APIs, email validation doesn’t need to be a complex solution. Sending an email to the passenger upon sign-up or when entering booking information to request verification is the most common and effective solution.

I also share my thoughts on how airlines can maximise deliverability and engagement across email and other passenger channels, in our on-demand webinar.

A shared responsibility

As a transactional email partner, 15below ensures infrastructure, authentication and sending practices meet industry best standards. However, the quality of the underlying passenger data sits upstream.

Improving validation processes is therefore a shared responsibility across commercial, digital and operational teams.

If you would like to review your bounce rates, understand current thresholds or explore validation best practice, please don’t hesitate to get in touch and speak with one of our experts. We are happy to support a deeper review of how bad data is impacting your notifications. 

Operational communication only works when the data behind it is reliable. And in disruption, reliability is everything.