How to block emails in Outlook and Microsoft 365 (Office 365)

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Brandon Lee

Brandon Lee has been in the IT industry 15+ years and focuses on networking and virtualization. He contributes to the community through various blog posts and technical documentation primarily at Virtualizationhowto.com.

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Blocking senders in Outlook

First, open the Outlook desktop app and head to your inbox or junk email folder. Take note of the senders you want to block. You will need their email addresses for the subsequent steps.

Block an email sender

To block an email sender, select the unwanted email in your inbox. Next, click the Home tab in the menu bar. Then look for the "Junk" dropdown menu and select Block Sender. This action will block the sender's email address, ensuring that future messages from this sender are automatically redirected to the junk email folder. You can also simply right-click a received email in your inbox and select Junk to navigate to the same menu options.

Blocking a sender using the Outlook desktop client

After you click the Block Sender option, a dialog box pops up, noting that you have blocked the sender.

Message has been added to your Blocked Senders list

Viewing junk email options

If you're wondering where to view the blocked senders and other options, click the Junk E-mail Options menu item on your Junk menu.

Launching junk email options

You will see tabs for options: Safe Senders, Safe Recipients, Blocked Senders, and International. You can also manually add entries from this dialog box.

Viewing junk email options

Blocking emails in the Outlook Web App

Open a web browser and sign in to your Microsoft account. Then navigate to the Outlook web app to access your email inbox.

Block senders from the email window

Identify an unwanted email from the sender you wish to block. You can right-click any email and see the option to block. If you choose Block sender, future emails will be automatically redirected to the junk folder.

Blocking an email sender using the Outlook Web App

Blocking emails and domains from Microsoft 365 Defender

Exchange admins can also block emails and domains from Microsoft 365 Defender before they reach the end-user client. You can remove the block after a specific time interval or leave the block in place indefinitely.

Blocking domains and addresses using Microsoft 365 Defender

Other excellent email security options are found in the Tenant Allow/Block Lists. These include the following:

• Domain & addresses—As shown, you can block email domains and specific addresses you don't want your users to receive email from.
• Spoofed senders—When senders spoof email addresses, they appear to be users in one of your organization's domains. Here, you can block specific domains, addresses, and even IP addresses that are spoofing your domains.
• URLs—Attackers often use URLs to deliver malware. You can block these on the URLs tab.
• Files—Block specific files and file patterns from being delivered via email.

Blocking domains addresses spoofed senders URLs and files

Tips for controlling unwanted email

• Utilize Outlook's rules feature—Outlook rules can be powerful. You can create custom filters for managing incoming email messages to automatically move or perform certain actions on emails that match the rules, keywords, or other characteristics.
• Don't use your main email address—When signing up for events and other free resources, don't give out your main email address. Create a free email address you use for signing up for events and other resources. This way, your main email address is not exposed to potential spam lists.
• Unsubscribe from unwanted email lists—One way to reduce unwanted emails is to unsubscribe from the mailing lists you may find yourself on. When making purchases, signing up for events, etc., your email address can be added to mailing lists. Using the unsubscribe link at the bottom of an email is a great way to take the address off a list.
• Block entire domains—If there is a specific domain from which you receive a large quantity of spam or other unwanted emails, block the entire domain "@domain.com" instead of each individual address.
• Review your junk email—When fighting spam and other unwanted emails, there is a possibility that legitimate emails will be categorized as spam or match other rules you have in place. Therefore, review your junk folder often to ensure it contains only unwanted emails.

Wrapping up

Blocking emails in Outlook 365 is a straightforward process that helps maintain a clean, organized inbox. You can effectively block senders, manage your blocked sender's list, and block entire domains, files, URLs, and spoofed addresses. Review your junk email folder often, and stay vigilant when dealing with unknown senders and suspicious emails, as they may contain malicious content.

By blocking unwanted emails and managing your blocked sender's list, you can help keep your Outlook inbox free of many unwanted emails and focus on legitimate email communications. Whether you're using the Outlook desktop app, Web App, or mobile app, these tips and tricks will help you stay on top of spam and ensure a smoother email experience.