Stop Spam! Easy Steps to Configure Office 365 Spam Filters

We all rely on email for both personal and professional purposes. Over time, we’ve noticed that almost every app or service requires users to provide their email addresses to access their features. As a result, we accumulate a large number of junk emails, which can clutter our inboxes and disrupt workflow. Additionally, Spam emails can be a huge problem for businesses, leading to cluttered inboxes, missed important messages, and sometimes serious security breaches like phishing or malware attacks. Office 365, now known as Microsoft 365, provides robust tools to help you manage and reduce the amount of spam entering your organization. The built-in Office 365 spam filter is highly effective, but configuring it properly is essential to ensure optimal performance and minimize the risk of harmful spam.

This article will walk you through the process of configuring the Office 365 spam filters in easy steps. Before deleting or applying filters to spam emails, we recommend users back up their Office 365 accounts. This can easily be done using the Regain Office 365 Backup Tool.

Precautions to Take Before Applying Office 365 Spam Filters

Applying a Microsoft 365 spam filter isn’t just about preventing future spam emails. In this guide, we’ll show you how to locate and remove spam emails effectively. However, be cautious when deleting junk mail, as it can sometimes lead to the accidental loss of important emails. That’s why IT experts recommend backing up your Office 365 account before making significant changes. This precaution helps safeguard your data from loss or corruption. Users can easily back up large Office 365 inboxes with the Regain Office 365 Email Backup Tool. This user-friendly software allows you to save Office 365 emails in various file formats such as PST, MBOX, EML, EMLX, MSG, and vCard Format.

Steps to Backup Office 365 Account

1. Install and launch the Office 365 Backup Tool as an administrator.
2. Enter your Office 365 Credentials and click on the Connect to Server button.
3. Select the Desired Files/Folders from the tree structure and click on the Next button.
4. Choose the Saving Format and click on the Next button to proceed further.
5. Finally, click on the Browse button to define the Destination Path and clock on the Next button to start the backup of your Office 365 mailboxes.

Why Office 365 Spam Filtering is Crucial

Before exploring the steps to configure the spam filter, it’s essential to understand why spam filtering is important for any business. Spam is more than just unwanted promotional emails—these messages can include:

• Phishing Scams: Emails that appear legitimate but steal sensitive information.
• Malware Attachments: Files designed to infect your system and gain unauthorized access.
• Fraudulent Links: Links that direct users to malicious websites.
• Email Spoofing: Emails that appear to come from trusted sources but are sent by malicious actors.

Moreover, reducing spam improves security, ensures productivity, and saves time spent manually sorting through irrelevant or dangerous emails.

Some Office 365 Built-in Spam Protection Features

Office 365 is a very versatile Email service. It offers its users with many useful features and filters. Moreover, Office 365 comes with a set of default anti-spam features, including:

• Anti-phishing protection: Designed to prevent phishing attacks.
• Malware filtering: Blocks attachments and links that contain viruses or malicious content.
• Bulk mail filtering: Automatically moves bulk and promotional emails to the spam folder.
• IP address filtering: Blocks emails from known spam-producing IP addresses.

While testing Office 365’s spam filters, we found that the default protections work well for personal email accounts. However, if you’re using a business email or handling large volumes of emails, it’s advisable to apply custom configurations for better protection.

Learn more about our Professional Regain Office 365 to Gmail Migration tool

Methods to Configure the Office 365 Spam Filters

After extensive research, we have identified the most effective methods for applying Office 365 junk filters to your account. The following section provides all the information you need on how to set up and configure Office 365 spam filters.

Method 1: Access the Office 365 Admin Center

To begin configuring your spam filter, you’ll need to access the Microsoft 365 Defender portal through the Office 365 Admin Center.

1. Log in to your Office 365 account with an admin user profile.
2. Navigate to the Microsoft 365 Defender.
3. On the left-hand navigation, select Policies & Rules > Threat Policies.

From here, you can manage settings for spam filtering, phishing detection, and more.

Method 2: Review and Adjust Default Spam Filter Policies

Office 365’s spam filter uses Exchange Online Protection (EOP) as the core tool to detect and block spam. EOP comes with default spam filter policies, but you can customize them as needed. Here’s how:

1. Under the Policies section, choose Anti-spam policy.
2. Select the Default spam filter policy and click on Edit.

This brings up the default configuration, where you can make specific adjustments to better fit your organization’s needs.

Method 3: Configure Custom Spam Filter Policies

To increase the spam detection accuracy for your organization, you may want to create and customize additional policies. Here’s how to configure a custom spam filter policy:

1. In the Microsoft 365 Defender portal, go to Policies & Rules > Threat Policies > Anti-Spam.
2. Click on Create Policy and name your custom policy.

Under this custom policy, you can set various filters and thresholds to control spam detection more precisely. Some policies are as follows:

Policy 1: Block Specific Senders or Domains

If you consistently receive spam from certain email addresses or domains, you can block them:

• In the Allow/Block section, add the email addresses or domains that you want to block.
• You can add individual addresses (e.g., spammer@example.com) or entire domains (e.g., @example.com) to the block list.

Policy 2: Adjust Spam Confidence Levels (SCL)

Spam Confidence Level (SCL) is a score that Microsoft assigns to emails to determine the likelihood of them being spam. The higher the score, the more likely it is to be spam. Here’s how to adjust the thresholds:

• Set the thresholds for what gets delivered to the inbox, sent to the junk folder, or outright rejected.
• Use SCL 1-4 for legitimate emails, SCL 5-6 for emails that should go to the junk folder, and SCL 7-9 for emails that should be blocked entirely.

Policy 3: Enable Spoof Intelligence

Spoofing occurs when a sender pretends to be someone from your organization or a trusted domain. You can enhance your spam filter by enabling Spoof Intelligence:

• In the Anti-phishing Policies section, activate the Spoof Intelligence feature.
• This helps detect emails with suspicious spoofing attempts and automatically blocks them.

Method 4: Quarantine Suspicious Emails

Office 365’s quarantine feature helps to isolate emails that seem suspicious but aren’t definitively spam. You can review quarantined emails and decide whether they should be allowed through or remain blocked. Here’s how to configure it:

• Under Policies & Rules > Threat policies, go to Anti-spam policies.
• Scroll down to Quarantine settings.
• Choose to quarantine emails with High Confidence Spam (SCL 7-9) and suspicious phishing attempts.

Quarantined emails can be released manually if they are mistakenly identified as spam.

Method 5: Fine-Tune Phishing Protection

Phishing is one of the most dangerous forms of spam, as it can lead to data theft and security breaches. Office 365 offers robust phishing protection features, but you can take extra steps to fine-tune it:

• Go to Anti-phishing policies.
• Enable the Impersonation Protection feature to detect attempts at impersonating key executives and employees.
• Set up Action policies for phishing attempts, such as sending phishing emails to quarantine or rejecting them outright.

Method 6: Configure Microsoft Defender for Office 365 Protection

For businesses that require a higher level of protection, you can enable Advanced Threat Protection (ATP), which provides deeper inspection of potentially dangerous content. ATP can help block malicious links and attachments before they even reach your inbox. The steps to enable ATP are as follows:

• In the Microsoft 365 Defender portal, go to Policies & Rules > Safe Attachments and Safe Links.
• Set up policies to scan attachments and links in emails for malware.
• Enable ATP for both incoming and outgoing emails to ensure maximum protection.

Method 7: Configure SPF, DKIM, and DMARC for Better Email Protection

• SPF verifies authorized sending servers.
• DKIM adds a cryptographic signature to outgoing messages.
• DMARC helps receiving systems determine what to do when authentication fails.

Additional Practices to Prevent Office 365 Spam Emails

In addition to configuring Office 365’s spam filter, there are a few best practices you should follow to further reduce the impact of spam on your business.

Practice 1: Educate the Employees

No matter how effective your spam filter is, employees must be aware of email security best practices. Regular training can help them recognize phishing emails, malicious links, and suspicious attachments. A few points to cover include:

• Never click on links or download attachments from unknown sources.
• Report suspicious emails to IT immediately.
• Regularly update passwords and use multi-factor authentication.

Practice 2: Monitor Email Flow and Adjust Policies as Needed

Spam filtering is not a one-time task; it requires continuous monitoring and adjustment. Use Microsoft 365’s Message Trace feature to keep track of email flow. Additionally, this feature can identify any gaps in your spam protection policies. If spam levels increase, revisit your custom policies to adjust thresholds and blocked addresses.

What to Do When Legitimate Emails Go to Spam

1. Check the Junk Email folder and quarantine.
2. Review the message’s filtering details.
3. Check SPF, DKIM and DMARC authentication.
4. Submit legitimate messages to Microsoft through the Defender submission process.
5. Use allow entries only when necessary.
6. Avoid broad mail-flow bypass rules.

Conclusion

Before deleting unwanted emails or making major changes to Microsoft 365 mailbox data, consider creating a backup of important emails and attachments. The Regain Office 365 Mailbox Backup Tool can export Microsoft 365 mailbox data to formats such as PST, EML, MSG and other supported formats.

Frequently Asked Questions

Q1. How do I configure the spam filter in Microsoft 365?
Ans. Sign in to the Microsoft Defender portal and open Email & collaboration > Policies & rules > Threat policies > Anti-spam. From there, administrators can review or configure anti-spam policies for their organization.

Q2. Does Microsoft 365 have a built-in spam filter?
Ans. Yes. Microsoft 365 automatically protects cloud mailboxes against spam using anti-spam policies and other email protection technologies.

Q3. How do I stop unwanted emails in Microsoft 365?
Ans. Review your anti-spam policies, block persistent spam senders or domains, use appropriate quarantine settings, and avoid unnecessarily broad allow lists. Microsoft also provides Standard and Strict preset security policies for stronger protection.

Q4. Why are legitimate emails going to spam in Microsoft 365?
Ans. Legitimate messages can be filtered because of authentication failures, sender reputation, message content, or other filtering signals. Check SPF, DKIM and DMARC configuration and use Microsoft’s submission tools to report false positives.

Q5. How can I find out why an email was marked as spam?
Ans. Administrators can use Message Trace to investigate the message and review the filtering event details and action taken by Microsoft 365.

Q6. Should I add a sender or domain to the Microsoft 365 allowlist?
Ans. Only when necessary. Broad allow entries can weaken email protection, so investigate the reason for the filtering first and use allow entries carefully.

Q7. How can I protect Microsoft 365 emails before deleting spam?
Ans. Before deleting unwanted emails or making major mailbox changes, create a backup of important mailbox data. The Regain Office 365 Backup Software can back up Microsoft 365 mailbox data to supported formats, helping preserve a separate copy of important emails and attachments.

Q8. Can Microsoft 365 protect against phishing and impersonation?
Ans. Yes. Microsoft 365 provides anti-spoofing protection, while Microsoft Defender for Office 365 adds capabilities such as user and domain impersonation protection, mailbox intelligence and phishing thresholds.