How to Block a Sender in Outlook 365

To block someone in Outlook 365, select one of their messages and choose the sender-blocking command in the version of Outlook you use. Outlook then diverts future messages from that address to Junk Email rather than deleting them. You will need access to the mailbox and the message or email address you want to block; the steps below cover Outlook for Windows, Outlook on the web, and Mac.

What You’ll Need

Access to your Outlook 365 mailbox in the Windows or Mac app, or in a supported web browser at Outlook on the web.
A message from the sender, or the sender’s exact email address. Blocking the address shown on a message is more reliable than guessing it from a display name.
If this is a work or school account, be aware that your organization may manage spam and blocked-sender settings centrally.

Step-by-Step

Find a message from the sender. Open your Inbox or another mail folder and locate an email that genuinely came from the address you want to block. You usually do not need to open it: selecting the message in the list is enough. If the sender’s display name is generic or unfamiliar, open the message and check its From address before taking action. Be cautious with suspicious email; do not open attachments or follow links just to identify the sender.
Block the address in new Outlook for Windows or Outlook on the web. Select the message. Look on the toolbar for Block or open the message’s context menu by right-clicking it, then choose the sender-blocking option, such as Block > Block sender. In some layouts the command is under the three-dot More actions menu or the Junk or Report menu. Confirm the block if Outlook asks. The precise placement can vary with window size and interface updates, but the command is attached to the selected message; use the toolbar search or menu rather than creating a rule if you want to block a sender.
Block the address in classic Outlook for Windows. Select the message in the message list. On the ribbon, go to Home > Junk > Block Sender. If the message is open in its own window, the same command is generally available from the message’s Junk menu. Confirm the prompt if one appears. Classic Outlook may show a confirmation that the sender was added to the Blocked Senders list. The menu wording and ribbon arrangement can differ slightly between builds, but look for Junk, not the command for marking a message as phishing.
Block the address in Outlook for Mac. Select the email, then look in the message’s context menu or the message menu for Block Sender or a similarly named block option. If you do not see it, open Outlook’s settings and go to the junk-email settings to add the address to the blocked list. Mac interface labels can differ between the newer Outlook experience and legacy Outlook, so use the settings route when the message menu does not offer a block command. Confirm the action if prompted.
Check that Outlook accepted the action. Look for a brief confirmation or revisit the blocked-senders list in settings. In Outlook on the web and new Outlook, open Settings (the gear icon), choose Mail > Junk email, and review Blocked senders and domains. In classic Outlook for Windows, the list is under Home > Junk > Junk E-mail Options > Blocked Senders. Mac settings include a junk-email or blocked-senders list; the location depends on the Outlook version. Check that the address is present and spelled correctly.
Test with a later message, if practical. A block normally affects incoming mail after it is applied; it does not remove earlier messages from the Inbox. If another message arrives from that exact address, check whether it is in Junk Email and whether the From address is actually the one you blocked. Avoid sending a test message to a person who is harassing or threatening you; a real later message or the list entry is enough to verify the setting.

Outlook for iOS or Android has a separate, touch-based layout. If you are using the mobile app, open or select the message and check its three-dot menu for a block-sender command. If the command is absent, add the address to the blocked list in Outlook on the web; the available options in mobile can depend on the account type and app version.

Common Mistakes

Blocking the display name instead of the address. Display names are easy to change and are not always unique. Check the full email address, especially when a message looks suspicious. A sender can also use a different address for each campaign, in which case blocking one address will not block the others.
Expecting blocked mail to disappear completely. Blocking normally sends future messages to Junk Email, where they remain until you delete them or Outlook’s retention settings remove them. It is not the same as deleting the current message, permanently erasing all past mail, or unsubscribing from a mailing list.
Choosing Report phishing when you only mean block. Use the block command to divert unwanted messages from a particular address. Report phishing is for messages you believe are trying to steal information or commit fraud; reporting can send information to Microsoft or your organization’s administrators and is a different action.
Blocking an address that you still need. A legitimate contact, billing notification, or automated service may use the address. Check the sender carefully before blocking it. If only a particular type of message is unwanted, an Outlook rule or the service’s unsubscribe option may be more suitable.
Assuming a block follows you to every mailbox. A blocked-senders list is associated with an account or mailbox, not with your name across all email services. If you have multiple accounts in Outlook, make sure you selected the message in the account where you want the block to apply.

Tips

Use unsubscribe for legitimate newsletters. For a mailing list you signed up for, use its unsubscribe link or Outlook’s unsubscribe option when available. Blocking may divert its email, but it does not tell the sender to remove your address from the list.
Block a domain only when appropriate. In Outlook on the web or new Outlook, the blocked-senders settings can let you add a domain as well as an address. A domain block can catch messages from multiple addresses at that domain, but it can also hide useful mail from that organization. Prefer a single address unless you are confident you want to block the entire domain.
Review Junk Email occasionally. A sender block can be too broad or an address can be added by mistake. Check the folder from time to time, especially after changing your list, and use Not junk or remove the address from the blocked list if a wanted message is being diverted.
Use a rule for more specific filtering. If you want to keep mail from a sender but move only messages with a certain subject or phrase, create a rule instead of blocking the whole address. Rules and block lists solve different problems: a rule can target message details, while a block generally targets the sender.
Keep evidence of serious abuse. If unwanted messages include threats, fraud, or repeated harassment, keep copies and use your organization’s reporting process or the relevant email provider’s abuse-reporting tools. Blocking can reduce incoming mail, but it is not a substitute for reporting a safety or security concern.

Troubleshooting

The Block command is missing. Confirm that a message is selected, then check the ribbon, right-click menu, and three-dot menu. The wording differs between classic Outlook, new Outlook, web, and Mac. If your organization manages the mailbox, an administrator may limit junk-mail controls. Try Outlook on the web or ask your IT support team which controls are available for your account.

Messages from the person still reach the Inbox. Check the exact From address on the new message and compare it with the blocked list. The person may be writing from another address, using a mailing service, or changing the address displayed to you. Also verify that the block was added to the correct mailbox. If the message is already in the Inbox, move or delete that existing message separately; applying a block does not necessarily act retroactively.

The blocked message appears in Junk Email. That is generally the expected result, not a failure. Outlook’s sender-blocking feature routes mail to Junk Email rather than guaranteeing immediate deletion. If you do not want to see it there, delete the message and review your Junk Email retention and cleanup settings, but do not assume that deleting one message removes the sender from the block list.

A wanted message is going to Junk Email. Open the blocked-senders list and remove the address or domain, then mark the message Not junk if that option is available. For a work or school mailbox, organization-level filtering may also be involved, so removing a personal block may not be sufficient. Ask your administrator to check the mail policy if the issue continues.

The list does not appear to sync across devices. Make sure each app is signed in to the same account and that you are not looking at a separate personal, work, or shared mailbox. Close and reopen Outlook or refresh the web page, then check the list again. Some settings can differ by account type or be controlled by an administrator; if the list remains inconsistent, manage it in the web version or contact support.

Frequently Asked Questions

Does blocking a sender delete their old emails?
No. Blocking generally affects future messages. Existing messages remain in the folders where they were delivered unless you move or delete them yourself.

Will the sender know that I blocked them?
Outlook does not normally send the sender a notification that you blocked them. They may still send email, but Outlook should route mail from the blocked address to Junk Email. A block does not prevent contact through other addresses or services.

Can I block someone without opening their email?
Usually, yes. Select the message in the message list and use the block command from the ribbon or context menu. If you need to verify the address first, inspect the sender details without clicking links or attachments.

Can I block an entire email domain?
In supported Outlook on the web and new Outlook settings, you can add a domain to the blocked-senders list. Be careful: this can divert legitimate mail from every address at that domain. If the option is missing, your account or organization may not support it.

How do I unblock a sender?
Open the blocked-senders list for the same mailbox, find the address or domain, and remove it. In Outlook on the web or new Outlook, start at Settings > Mail > Junk email. In classic Outlook for Windows, open Junk E-mail Options and select Blocked Senders. Menu locations on Mac depend on the version.

Is blocking the same as reporting spam?
No. Blocking targets future mail from an address or domain. Reporting junk or phishing flags a message for review and may help improve filtering or alert your organization. Choose the action that matches the problem, and use your organization’s security process for suspicious work email.

Try it: the Date Difference Calculator: days, months, years and weekdays between two dates, with the DATEDIF formulas.

More in How-to basics

Sources: Function behaviour and menu paths: Microsoft Support documentation for Excel. Method & sources

Spotted an error in this guide? Let us know.