How to block spam emails for good – according to a tech expert

Spam emails can be a real pain – potentially tricking you into handing over personal data and making it harder to spot the emails you actually want to see.

Typically, the advice would be to block the sender and report the message as spam. While this can work for individual instances, it won’t stop spam when the sender constantly rotates the address they send from.

Thankfully, our experts at Which? Tech Support how found that creating custom rules or filters in your email app of choice can help block junk before it even appears in your inbox. Keep scrolling to learn how it's done.

Jump to: Block Gmail spam | Block Outlook spam | Block Yahoo spam | Block BT Mail spam | Block Apple Mail spam

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Each month, we feature one of the most popular questions answered by our Tech Support team.

Question of the month: what's the best way to deal with unwanted emails?

'Recently, I’ve been receiving a lot of spam – dozens of messages a day – in my inbox. They’re all offering the same thing: free bitcoin. I keep blocking them, but they still come through. How can I stop this?'

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How to set up email rules

Many spam senders constantly change or rotate their email addresses (eg from 123@outlook.com to 1234@outlook.com) to try and get around individual blocking. You can continue to block them, but it becomes an endless cycle without any real impact.

Instead of blocking addresses one by one, you can create custom rules or filters to automatically delete or move these emails without any manual intervention.

For example, if the subject line of a recurring spam email is ‘free bitcoin’, you can create a rule that automatically deletes any email with that subject – regardless of the sender’s address. These rules can be as specific or as broad as you like. For instance, you could filter by the exact phrase ‘free bitcoin’ or simply use a keyword like ‘bitcoin’.

But be careful when using keywords – you don’t want to accidentally filter out legitimate emails.

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To block spam on Gmail, try this:

1. Open up your Gmail inbox.
2. In the search bar at the top of your screen, select Show search option, which is the icon featuring three lines.
3. In the Subject box, type in a phrase to filter out. For example, you could enter 'free bitcoin'.
4. Click Create filter at the bottom of the drop-down menu.
5. On this next screen, you'll be asked what should happen to emails that feature your search phrase. Simply tick Delete it.
6. Finally, select Create filter.

To block spam on Outlook, try this:

1. Open up your Outlook inbox.
2. Click the Settings cog wheel in the top-right corner of your screen.
3. Choose Email and then, under Layout, select Rules.
4. Click the Add new rule box.
5. Give the rule a name (eg bitcoin spam rule)
6. Under Add a condition, open the drop-down menu, select Subject includes and type in 'free bitcoin' in the Enter words to look for field.
7. Under Add an action, open the drop-down menu and select Delete.
8. Click Save to finalise your changes.

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To block spam on Yahoo, try this:

1. Open up your Yahoo inbox.
2. Click the Settings cog wheel in the top-right corner, then select More settings.
3. Choose Filters and click Add new filters.
4. You now need to give your filter a name – 'bitcoin spam rule', for example.
5. Under Set rules, select Subject > Contains > 'free bitcoin'.
6. Under Choose the folder to move it to, select Deleted items.
7. Click Save.

To block spam on BT Mail, try this:

1. Open up your BT Mail inbox.
2. Click the drop-down menu next to your username (top-right corner) and select Settings.
3. Select Mail > Rules > Add.
4. Under the Condition section, select Subject line contains and enter 'free bitcoin'.
5. Under the Set rule action list, select Discard.
6. Click Save.

To block spam on Apple Mail, try this:

1. Open up the Mail app on Mac.
2. In the menu bar, choose Mail > Settings (or Preferences, depending on your macOS version).
3. Select Rules > Add Rule.
4. Give your rule a name – for example, ‘Bitcoin spam’.
5. Under If any/all of the following conditions are met, choose Subject > Contains, and type in 'free bitcoin'.
6. Under Perform the following actions, select Delete message (or Move message to Junk).
7. Click OK.

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This article was updated 16 May 2025 to include Apple Mail.