How to Block a Sender in Outlook Online (and Unblock Them)

Open the email, click More actions (…) at the top right of the message, point to Block and choose Block plus the sender’s name. Or add the address under Settings > Mail > Junk email.

In this tutorial, I’ll show you how to block a sender in Outlook online both ways, how to block a whole domain, how to unblock someone, and what to check when Block is greyed out.

Block a sender from the message in Outlook on the web

I tested this in a Microsoft 365 work mailbox for my made-up business, Bluebird Landscaping Co. This is the fastest route when the unwanted email is already sitting in your inbox.

1. Open the email from the sender you want to block.
2. Click More actions (…) at the top right of the message, not the toolbar above the list.
3. Point to Block.
4. Choose Block followed by the sender’s name.

The same submenu also has Never block. That’s the opposite action, so read the line before you click. I stopped at the menu for my test sample.

Microsoft says a blocked sender’s messages are moved straight to your Junk Email folder. If you’d rather sort mail into a folder than block it, an inbox rule in Outlook Online is the gentler option.

Report junk or phishing instead of blocking

Right above Block in that menu sits Report. It opens two choices: Report junk and Report phishing.

Use Report phishing when an email pretends to be your bank or IT team and asks for a password. I didn’t click either option in my test, so I can’t tell you exactly what each one changes in your settings.

Not sure who really sent a message? Here’s how to show the full sender email address before you decide.

Add an address or a whole domain in Junk email settings

Settings is the better route when you want to block someone before they email you, or block every address at one domain.

1. Click the Settings gear at the top right. In a narrow window, it sits in the … menu next to the bell.
2. Go to Mail > Junk email.
3. Under Senders, open the Blocked senders and domains tab.
4. Click + Add blocked sender.
5. Type an address such as lawn-deals@example.com, or just example.com to block the whole domain, and click OK.
6. Click Save at the bottom of the page.

The address shows in the list as soon as you click OK. I still clicked Save before closing Settings, and the entry was there when I looked again.

The tab’s own text says these senders also shape auto-complete suggestions and other people features in Microsoft 365. Microsoft adds that a blocked account won’t show up when you search for people in Teams, unless you’ve already chatted with it there.

Junk folder filling up after a while? Check your Outlook storage space to see how much room it takes.

Unblock a sender or edit the blocked list

Go back to Settings > Mail > Junk email > Blocked senders and domains. Hover over an entry and two icons appear.

• Pencil: fix a typo in the address or domain.
• Trash can: remove the entry, which unblocks that sender.
• Save: click Save at the bottom when you’re done.

Want someone’s mail to always skip Junk? Add them on the Safe senders and domains tab next door instead. Both tabs sit on the same page, so check each one when an expected email goes missing.

When Block is greyed out or blocking is not enough

• It’s your own message. On emails I’d sent to myself, Report and Block were greyed out.
• The sender is a coworker. Microsoft says people in your organization’s address list can’t be added to the blocked list in classic Outlook, so talk to your admin about internal mail.
• Your list is full. The blocked and safe senders lists hold up to 10,000 addresses or domains. Blocking whole domains saves space.
• Spam still lands in your inbox. Under Incoming mail handling, Standard moves possible junk to Junk Email, while Strict only delivers mail from your safe senders and domains to the inbox.

Strict is a big switch, so check your safe senders first. Gmail user too? Here’s how I stop spam on Google Drive.

On Android, iPhone and the new Outlook for Windows

Microsoft’s help for the mobile apps says you select the email and then pick Junk, Phishing or Block Sender as needed. I didn’t test the apps for this post.

If you use the new Outlook for Windows with a Gmail, Yahoo or iCloud account added, Microsoft says it can’t block senders there. Block them with that email provider instead.

More Outlook Online fixes worth a look

• Make an email confidential in Outlook Online
• Set up automatic replies
• Sort emails by size in Outlook
• All Outlook Online tutorials

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