How Can You Stop Spam Mail? A Practical Guide for UK Businesses

22 January 2025

Spam mail is one of those daily frustrations that most of us have simply learnt to live with, but it doesn't have to be that way. Beyond being an annoyance, unwanted email can pose genuine risks to your business: phishing links, malware attachments, and social engineering attempts often arrive dressed up as ordinary junk. Whether you're wondering how to stop junk email piling into your inbox or you're trying to understand the best way to block spam emails across your organisation, this guide will walk you through the practical steps you can take right now.

What is Spam Mail?

'Spam mail', sometimes called 'junk email', refers to unsolicited messages sent in bulk, typically for commercial or malicious purposes. Not all spam is dangerous; plenty of it is simply unwanted marketing from companies you've never heard of. However, a significant proportion of spam is deliberately crafted to deceive, containing:

• Phishing links designed to steal login credentials or financial information
• Malware attachments that can infect devices when opened
• Fake invoices or delivery notifications intended to trick staff
• Advance-fee fraud and other financial scams

For businesses, the stakes are higher. A single employee clicking a malicious link can expose an entire network to compromise. That's why managing spam isn't just about tidying up your inbox; it's a fundamental part of good cybersecurity practice.

How to Block Spam Emails: Step-by-Step by Platform

The good news is that most email clients include built-in tools to help you manage and reduce spam. Here's how to use them.

How to Block Spam in Outlook

Microsoft Outlook, whether you're using it as part of Microsoft 365 or the standalone desktop application, has a robust junk mail filter. Here's what you can do:

• Right-click any suspicious email and select Junk > Block Sender. This immediately prevents further messages from that address.
• Go to Home > Junk > Junk E-Mail Options to adjust your filter level. Setting it to 'High' captures more spam, though occasionally it may catch legitimate emails too.
• Use the Safe Senders and Blocked Senders lists to fine-tune what gets through.
• Create Rules (Home > Rules > Manage Rules & Alerts) to automatically move, delete, or flag emails from certain senders or containing specific words.

For organisations running Microsoft 365, there are additional controls available through the Microsoft Defender portal, including anti-spam policies, safe links, and safe attachments, though configuring these is best handled by your IT team or managed service provider.

How to Stop Junk Email in Gmail

Gmail's spam filtering is generally strong out of the box, but there are steps you can take to improve it further:

• Open the email, select the three-dot menu, and choose Block Sender. Future emails from that address will go straight to spam.
• Click Report Spam (the '!' icon) to help train Gmail's filters the more spam you report, the better it becomes at detecting similar messages.
• Use Filters and Blocked Addresses (Settings > See all settings > Filters) to create custom rules: automatically archive, delete, or label emails matching certain criteria.
• For Google Workspace users, your administrator can set organisation-wide spam policies and configure enhanced pre-delivery message scanning.

Blocking Spam on Other Platforms

Most modern email clients, including Apple Mail, Outlook.com, and mobile apps, follow a similar pattern. Look for a 'Block Sender' or 'Mark as Spam' option in the message menu. The table below gives a quick overview:

Best Email Filters for Business

Blocking individual senders is useful, but it's a reactive measure you're always one step behind whoever is sending the spam. For businesses, a more robust approach involves implementing email filtering at the gateway level, before messages ever reach your users' inboxes.

Effective business-grade email filtering typically includes:

• Spam and malware detection that analyses incoming messages in real time
• Domain reputation checks that flag emails from known bad actors
• Attachment sandboxing, which tests suspicious files in an isolated environment before delivery
• Impersonation and spoofing protection, which catches emails that mimic trusted senders
• Data loss prevention (DLP) controls to stop sensitive information leaving your organisation via email

At Renaissance, our Total Security Suite includes advanced hardware and software protection designed to help reduce exposure to email-borne threats before they reach end users. As part of our Managed Cyber Security Services, we can help configure and manage email security as part of a layered defence strategy — meaning your team isn't reliant on manually blocking each spam sender one by one.

We also offer email archiving and journaling services, which are increasingly important for businesses with compliance obligations under UK GDPR and industry-specific regulations.

Why Am I Getting So Much Spam?

If your inbox has been flooded recently, there are a few common reasons:

• Your address was harvested from a public-facing website, forum, or social media profile
• A service you signed up for experienced a data breach, exposing your email address
• You responded to a spam email previously (even unsubscribing from a malicious list can confirm your address is active)
• Your domain lacks proper authentication records (SPF, DKIM, DMARC), making it easier for spammers to spoof your address

One important note: avoid clicking 'unsubscribe' on emails you don't recognise. For legitimate marketing emails, this is perfectly fine. But for unsolicited spam from unknown senders, clicking 'unsubscribe' can actually confirm to the spammer that your address is active and monitored, which often results in receiving even more spam.

If you believe your email address or your organisation's domain has been compromised, it's worth speaking to your IT support team as soon as possible.

How to Reduce Spam at an Organisational Level

For businesses looking to take a more systematic approach, consider the following:

• Configure SPF, DKIM, and DMARC records on your domain. These email authentication standards help prevent spammers from sending messages that appear to come from your domain.
• Train staff to recognise spam and phishing attempts and to report suspicious emails rather than engage with them.
• Use alias or role-based email addresses for sign-ups and public-facing contact forms, keeping primary staff addresses off public-facing pages where possible.
• Regularly audit your email environment to identify unusual sending patterns that might indicate a compromised account.
• Ensure your email platform is kept up to date, particularly if you manage your own mail server.

These measures won't eliminate spam entirely no solution can but they significantly reduce your exposure and make your business a less attractive target.

Need Help Managing Email Security for Your Business?

Managing spam effectively is an important part of maintaining a secure and reliable business email environment. If your team is spending time managing unwanted email or you're concerned that your current email security isn't keeping pace with the threats, Renaissance can help.

We provide Managed Cyber Security Services for small and medium-sized businesses across the UK, including email security as part of a broader, layered approach to protecting your organisation. Get in touch with our team to find out how we can help keep your inbox and your business safer.

Frequently Asked Questions

How do I block unwanted emails on Gmail?

Open the email, click the three-dot menu in the top right corner, and select 'Block [sender name]'. You can also click the spam icon (!) to report the message and help train Gmail's filters. For more granular control, use Filters and Blocked Addresses in your Gmail settings.

Why am I getting so much spam all of a sudden?

A sudden increase in spam often follows a data breach where your email address was exposed or because your address has been added to a harvested list. It can also happen if you've recently replied to or unsubscribed from a suspicious email, which can confirm to spammers that your address is active. If the volume is unusual or the emails appear targeted, contact your IT team.

Is it safe to unsubscribe from spam emails?

For emails from genuine organisations, retailers, or newsletters you signed up for, using the unsubscribe link is perfectly safe and usually effective. For unsolicited emails from unknown senders, however, it's better to mark the message as spam and delete it without interacting with it.

What is the best email filter for a small business?

The right solution depends on your email platform and business size. For Microsoft 365 users, Microsoft Defender for Office 365 provides strong built-in protection. Businesses requiring more comprehensive filtering, including gateway-level scanning, sandboxing, and archiving, may benefit from a managed email security solution. Speak to your IT provider about what's most appropriate for your setup.