Why keeping your email server updated matters

According to Software Security Patch Management — A Systematic Literature Review of Challenges, Approaches, Tools and Practices, the majority of cyberattacks in the wild exploit known vulnerabilities for which a patch had already been released. The problem isn't a lack of fixes, it's a failure to apply them in time. Two recent examples display this theory:

In December 2025, TechRadar reported that SmarterMail, a widely used email server platform, was found to contain a maximum-severity vulnerability that allowed attackers to remotely execute code with no credentials and no user interaction. The flaw had been quietly patched months earlier but because so many organizations hadn't applied the update, an estimated 16,000 internet-exposed servers remained vulnerable at the time of public disclosure. As TechRadar noted, many cybercriminals use patch announcements as a roadmap, specifically targeting organizations that are slow to update.

The pattern repeated itself with Microsoft Exchange. Writing in "Thousands of Microsoft Exchange servers remain unpatched against major threat — here's what to do to stay safe", Sead Fadilpašić reported that nearly 29,000 Exchange servers remained exposed online roughly a week after Microsoft disclosed and patched a high-severity flaw in hybrid Exchange deployments. The vulnerability, described as an improper authentication bug, could allow an attacker with admin access to escalate privileges from an on-premises server into a connected cloud environment, potentially without triggering detectable audit logs.

Outdated servers get flagged as spam sources

Major providers like Gmail, Outlook, and Yahoo regularly update their spam filters and authentication requirements. If your server isn't running current software and meeting up-to-date security standards, your legitimate emails can start landing in spam folders.

As the Australian Cyber Security Centre notes in How to Combat Fake Emails, "SPF and DMARC records are publicly visible indicators of good cyber hygiene." Email authentication protocols like DMARC, DKIM, and SPF are now considered baseline requirements, and outdated servers often struggle to properly implement or support the latest versions of these standards.

The ACSC guide explains that DKIM authentication is valuable because the mechanism travels with the email regardless of which mail servers it passes through. SPF remains important too, even with its known limitations, and receiving mail servers need to be correctly configured to honour all three protocols for the protections to take effect. This happens when your server software is up to date and correctly configured.

But even a fully updated server with all three protocols in place isn't a guarantee on its own. Research published in Weak Links in Authentication Chains: A Large-scale Analysis of Email Sender Spoofing Attacks tested 30 popular email services and 23 email clients and found that every single one was vulnerable to at least some form of spoofing attack, including Gmail and Outlook. The researchers identified 14 distinct techniques for bypassing SPF, DKIM, and DMARC protections, and demonstrated that combining multiple techniques could produce spoofing emails convincing enough to fool even technically experienced users. Their central finding noted that, "the authenticity of an email depends on the weakest link in the authentication chain."

What this means in practice is that authentication protocols work best when the entire chain is maintained. This means your server software, your configuration, and your settings all need to be current and correctly implemented. An outdated server doesn't just risk your own deliverability; it can become the weak link that attackers exploit to impersonate your domain.

Performance and reliability improve over time

Software developers continuously improve their products by fixing bugs, optimising how the system uses memory and processing power, and adding features that make administration easier. Without that ongoing investment, systems become a liability rather than an asset. Paubox's 60% of healthcare orgs admit email security failure report found that 83% of healthcare IT leaders say legacy email systems disrupt day-to-day operations, with 37% of IT teams spending 11–20 hours per week simply resolving secure email tickets. Regular updates keep your server efficient. They bring in optimisations that reduce load on your hardware and keep the experience fast and responsive for everyone using it.

Compliance

If your organization operates in a regulated industry such as healthcare, you likely have compliance obligations that tie directly to how your email infrastructure is maintained. Regulations like HIPAA include requirements around keeping software current and protecting data in transit and at rest. Running an outdated email server can put you in violation of these rules, even if nothing has actually gone wrong. According to Paubox's The 2026 Healthcare Email Security Report, 86% of healthcare IT leaders already worry their organization is falling short of that standard. Auditors will ask about your patching cadence. Cyber insurance providers require evidence of regular updates before they'll issue or renew a policy. The cost of non-compliance is fines, lost coverage, or reputational damage.

Making updates a routine

A few steps can make it a manageable routine:

• Subscribe to security advisories from your email software vendor so you know when updates are available and how urgent they are.
• Schedule a regular maintenance window to review and apply updates.
• Test updates in a staging environment first if possible, especially for major version upgrades.
• Keep backups current so that if an update causes an unexpected issue, you can roll back quickly.
• Document what you've done.

Patching isn't purely a technical task, it involves coordination across teams, competing priorities, and organizational policies that can slow things down. The systematic literature review identifies this as one of the most underappreciated challenges in patch management; the human and organizational side of keeping systems current. Building clear ownership, defined roles, and a regular communication rhythm around updates is just as important as the technical work itself.

On the authentication side, the ACSC is clear about starting with implementing DMARC, even if only in a monitoring mode configuration. The research in Weak Links in Authentication Chains notes that the goal isn't just to have SPF, DKIM, and DMARC in place, it's to ensure every part of the chain is properly implemented and kept current, because a single weak link is all an attacker needs.

Read also: Inbound Email Security

FAQs

Can small businesses handle email server updates without dedicated IT staff?

Many small businesses use managed email hosting providers who handle updates automatically, making in-house IT expertise less of a requirement.

How long does a typical email server update take to complete?

Most routine patches can be applied within a maintenance window of one to two hours, though major version upgrades may require more planning and downtime.

What's the difference between cloud-hosted and on-premises email servers when it comes to patching?

Cloud-hosted email services handle patching on your behalf, while on-premises servers place the responsibility for updates on your own team.

Are open-source email servers safer or riskier than commercial ones from an update standpoint?

Open-source servers benefit from community scrutiny but require users to actively monitor and apply updates themselves, whereas commercial vendors often provide more structured update notifications and support.

What should you do if a critical update breaks something in your email environment?

Having tested backups and a rollback plan in place before applying any update is the most reliable way to recover if something goes wrong.