Exchange trouble? Start with the bit you can control: your contact data

When email systems experience problems, marketing teams can quickly find themselves asking the same questions. Have our emails gone out? Are customers receiving them? And why are delivery figures suddenly looking different?

Recent problems affecting Microsoft Exchange Server have highlighted just how dependent businesses are on reliable email infrastructure.

But while server updates and technical outages are largely outside a marketer's control, there's one area businesses can take responsibility for: the quality of their contact data.

Invalid email addresses, outdated customer records and poorly maintained mailing lists can create avoidable problems, even when everything else is working as expected.

And when delivery is already under pressure, the last thing you need is another reason for emails not to reach their destination.

What happened with Microsoft Exchange Server?

In October 2026, Microsoft acknowledged problems affecting some organisations using on-premises Exchange Server following Windows Server updates.

Reported issues included users being unable to access Outlook on the web (OWA), growing email queues and delays in sending messages.

The problems did not affect every Exchange Server installation, and Microsoft confirmed that the issue related to Windows Server updates rather than Exchange Server security updates themselves.

On 10 November, Microsoft confirmed that its November Windows Server updates addressed the problem.

The disruption offers a useful reminder for businesses: email delivery depends on several different systems working properly.

And while technical teams handle infrastructure problems, marketing and CRM teams have their own part to play in keeping communications reliable.

Read Microsoft's explanation of the Exchange Server issue.

Why email delivery problems aren't always easy to diagnose

When an email campaign underperforms, it's tempting to assume there's something wrong with the platform.

But delivery problems can have several causes.

An email might be delayed because of a server issue. It might bounce because the recipient's address no longer exists. Or it might be rejected because of sender authentication or reputation problems.

These are different issues requiring different solutions.

For marketing managers and agencies sending thousands of emails, an outdated mailing list can make performance reporting harder to interpret.

If a campaign contains hundreds of invalid addresses, those failures create additional noise when you're trying to understand what's happening.

Email validation won't fix a server outage. But it can help you rule out avoidable problems with your contact list.

Why validate email addresses before your next campaign?

Email addresses don't stay accurate forever.

People change jobs, businesses close, domains expire and customers abandon old accounts.

A contact list that performed well six months ago may contain addresses that are no longer suitable for outreach.

Regular email validation helps businesses identify potential problems before sending campaigns.

The benefits can include:

• Fewer avoidable bounces: Identifying invalid addresses before they enter a campaign.

• Cleaner reporting: Making it easier to assess campaign performance without unnecessary list-quality errors.

• Less wasted effort: Reducing time spent preparing and sending communications to unusable addresses.

• Better database management: Highlighting records that may need updating, reviewing or removing.

Validation isn't a guarantee that every email will be delivered. Mailbox settings, spam filtering and server availability can still affect the outcome.

However, it gives marketing teams a more reliable starting point.

Five email data checks to make before your next send

You don't need to overhaul your entire CRM to start improving email data quality.

These five checks can help identify common issues before your next campaign.

1. Remove obvious formatting errors

Look for missing @ symbols, incorrect domain formats, unwanted spaces and other mistakes that make an email address invalid.

2. Validate your email list

Use an email validation service to identify addresses that appear invalid, undeliverable or otherwise risky.

Review uncertain results rather than automatically deleting every flagged address.

3. Review role-based and disposable addresses

Generic inboxes such as info@ or sales@ may be legitimate business contacts, but they aren't always appropriate for every campaign.

Disposable email addresses may also require additional review.

Decide how to handle these records based on your campaign's purpose.

4. Recheck older customer segments

If you haven't contacted a particular group for several months, consider validating those addresses before including them in a new campaign.

Also check existing unsubscribes and suppression records. An email address passing validation doesn't mean you have permission to contact it.

5. Add validation when collecting new contacts

Rather than repeatedly cleaning the same problems, consider validating email addresses when they're first entered into your CRM, website forms or customer database.

Catching errors earlier can reduce the amount of cleaning required later.

Email data accuracy and UK GDPR

Keeping customer information accurate isn't just about campaign performance.

Article 5(1)(d) of the UK GDPR sets out the accuracy principle, requiring personal data to be accurate and, where necessary, kept up to date.

The Information Commissioner's Office (ICO) explains that organisations should take reasonable steps to ensure the personal information they hold is correct.

For businesses using email addresses to communicate with customers, having appropriate processes to identify and address inaccuracies can support this responsibility.

However, email validation alone doesn't establish GDPR compliance.

Businesses must also consider lawful processing, marketing permissions, retention periods and individuals' rights.

You can read more in the ICO's guidance on the accuracy principle.

Start with a small email data cleanse

The recent Exchange Server problems demonstrate how quickly email communications can be disrupted by issues outside a business's control.

But your contact database doesn't have to be another source of uncertainty.

Before your next campaign, take a little time to check whether the email addresses you're relying on are still valid.

You don't necessarily need to clean your entire database at once. Start with a smaller segment, review the results and decide where regular validation would be most useful.

Reliable campaigns start with reliable contact data.

Data Soap offers email validation tools to help businesses identify potential problems in their contact lists.

Try Data Soap's £4.99 starter pack or speak to the team about your data validation requirements.

Explore Data Soap's pricing and starter pack.