How to set up the Outlook spam filter and customise it

Outlook includes a built-in spam filter that automatically removes incoming spam emails or moves them to the Junk folder. You can customise the filtering rules in the junk filter settings to match your personal preferences.

How to configure the Outlook spam filter quick guide

1. Go to the ‘Home’ tab.
2. Click ‘Junk’.
3. Select ‘Junk E-mail Options’ from the menu.
4. Set the protection level to either ‘Low’ or ‘High’ to enable the Outlook spam filter.

Available options for configuring the Outlook spam filter

Outlook provides several settings to manage spam. In addition to setting the overall filtering level, you can also block specific senders or define safe senders and recipients.

Setting up the standard spam filter

You can access the Outlook Junk Email Filter configuration via the ribbon in the ‘Home’ tab. The exact process depends on how your Outlook interface is set up. If you’re using the classic ribbon, first click the ‘Junk’ button (found in the ‘Delete’ category), then select ‘Junk E-mail Options’.

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In the simplified ribbon view, the ‘Junk’ button appears after clicking the three-dot icon:

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In the next window, enable the spam filter by selecting either ‘Low’ or ‘High’. Try both options over a few days or weeks to find the best fit. If too much spam lands in your inbox, switch to ‘High’. If too many legitimate emails—like newsletters you’ve subscribed to—are being flagged, switch back to ‘Low’.

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Defining safe senders and recipients

Outlook allows you to create a whitelist of trusted addresses. Any email not from an address on this list will be treated as spam. Be cautious when enabling this feature—emails from prospective customers or new contacts may be filtered out.

To activate the whitelist, select the ‘Only Safe Senders and Recipients’ option in the Junk Email Options. Then go to the ‘Safe Senders’ tab and enter the email addresses you trust. You can also tick the box labelled ‘Also trust email from my Contacts’ to automatically include your saved contacts.

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Adding blocked senders

The ‘Blocked Senders’ list shows all email addresses currently blocked. To manually add an address, click ‘Add’. You can remove any address by clicking ‘Remove’.

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Blocking specific country domains

Many spammers use email addresses with domain names from lesser-known countries, especially small island nations where domains are cheap to register. Under the ‘International’ tab, you can block emails from specific country domains that you’re unlikely to receive legitimate emails from.

Marking emails as spam manually

If a spam email isn’t automatically flagged, right-click it in your inbox, then choose ‘Junk’ followed by ‘Block Sender’.

How does a typical spam filter work?

Spam filters identify spam emails by looking for common content patterns like frequently used links or tracking pixels often embedded in spam messages. Known mail servers used for spam distribution are listed on greylists and blocked by email providers before the emails reach your inbox. These lists are powered by Domain Name System-based Blackhole Lists (DNSBLs), which are real-time blacklists of suspicious senders.

It’s important to train the Outlook spam filter to improve its detection accuracy. Don’t just delete spam emails that reach your inbox—mark them as spam instead. This helps the filter learn and become more effective. The same applies to messages incorrectly flagged as spam. You can also configure the Outlook filter to block specific email addresses permanently.