Best spam filter for Outlook and Office 365

The best spam filter for Outlook depends on which Outlook you mean. On a Mac or PC with an Outlook.com or Microsoft 365 account, Alrighty adds what Outlook's own filter lacks: phishing checks on your computer, a list of the scams and cold mail that got through, and one action that keeps a sender out. Outlook's built-in junk filter runs on Microsoft's servers for every account and is free. Safe senders and Blocked senders fix its mistakes. A company on Microsoft 365 gets the most from Microsoft Defender for Office 365. SpamSieve adds a filter to Outlook for Mac, but only in legacy mode.

Most pages for this search are written for classic Outlook on Windows, or for companies buying an email gateway. They tell you to open Junk E-mail Options and raise the protection level. That menu doesn't exist in the new Outlook, in Outlook on the web or in Outlook for Mac, and most of the tools they list run only on Windows. This page says which filter works with which Outlook app and which kind of account, and what's left when you read Outlook mail on a Mac.

If you're choosing a mail app for your Outlook account, see the best email app for Outlook accounts. For spam filters across iCloud and Gmail too, see the best spam blocker for Mac.

How we checked

We read Microsoft's support and Learn pages and each tool's own product, help and pricing pages on November 4, 2026, and every fact links to its source. Where a page didn't say something, such as a price, we say so instead of guessing. We didn't run spam through any filter. Alrighty is our app, and it is listed first.

Spam filters for Outlook at a glance

Filter	Price	Outlook accounts	Works in which Outlook	Where it filters	Who sets it up
Alrighty	14-day trial with no card, then Free or Pro	Outlook.com, Hotmail, Live, Microsoft 365	Its own app, in place of Outlook	Your computer; Clean up on its server	You
Outlook's junk filter	Free	Every Microsoft account	All, because it runs on the server	Microsoft's servers	On by default
Junk filter levels	Free	Any account in classic Outlook	Classic Outlook for Windows only	Your PC	You
Safe and Blocked senders	Free	Every Microsoft account	All; set in Outlook on the web	Microsoft's servers	You
Microsoft 365 advanced security	Microsoft 365 Personal or Family	Outlook.com, Hotmail, Live, MSN	All	Microsoft's servers	Automatic
Defender for Office 365	Included in some business plans, or an add-on	Microsoft 365 work and school	All	Microsoft's servers	Your IT admin
SpamSieve	$39.99 once	Any account in Outlook for Mac	Legacy Outlook for Mac only	Your Mac	You
Clean Email Screener	Paid plans; no prices shown	Outlook.com and others	All, because it works on the mailbox	Clean Email's servers	You
SpamTitan	By quote	Microsoft 365 organizations	All	SpamTitan's servers	Your IT team

Which Outlook do you have?

"Outlook" names several apps and two kinds of account, and the spam settings differ for each.

• Outlook.com, Hotmail, Live and MSN are personal Microsoft accounts. You manage junk settings on the web.
• Microsoft 365 work or school accounts sit in your company's Exchange Online. Your IT admin sets the main spam policy. You can add your own safe and blocked senders on top.
• Classic Outlook for Windows is the only app with the old Junk E-mail Options dialog and its protection levels.
• New Outlook for Windows and Outlook on the web share one set of junk settings: Settings, Mail, Junk email.
• Outlook for Mac has no protection level setting in the Microsoft help we found. Its junk handling comes from the server, and the feature list shows Block sender as available (Microsoft).

The filter that matters most for every one of them is the server's. It runs before any app sees the mail.

Alrighty: best spam filter for Outlook accounts in a desktop app

Alrighty is a desktop mail app for Mac, Windows and Linux that puts Outlook, iCloud and Gmail accounts in one inbox. Outlook.com, Hotmail, Live and Microsoft 365 accounts connect with Sign in with Microsoft. Outlook's junk filter keeps running on Microsoft's servers. Alrighty works on what gets past it.

• Phishing checks. New Inbox mail is checked on your computer as it arrives. A message that is sure to be phishing goes to Junk. A likely one stays, with a warning in the message. Our phishing checker guide lists the signs it looks for.
• Clean up. It lists the senders you probably don't want, such as scams, cold outreach and newsletters you never open, so you can stop them all at once. Outlook's filter has no such list.
• Stop mail. One action ends a sender's mail. It unsubscribes in every way the message offers, archives their mail, and moves their new mail out as it arrives. It unsubscribes only from senders whose mail passed DMARC and wasn't marked spam, so a scammer never learns your address is live.
• Filters. Cold sales mail comes from a new sender each time, so a block can't catch it. Describe the kind of mail in your own words, or set rules, and new Inbox mail that fits moves to Archive before the list shows it. Mail from people you've written to is never moved.

Where your mail goes. Your mail stays with Microsoft, and Alrighty keeps its copy on your computer. Your sign-in stays on your computer, encrypted with a key from your system's keychain. The phishing check and rule filters run on your computer. A filter you describe in words asks an AI model through Alrighty's server, signed in only. Clean up sends each sender's address, three facts the receiving server found, and up to 3 of their newest emails (2,000 characters each) to Alrighty's server, which asks an AI model to sort them. If your company has rules about work mail and AI, check them before you add a work account.

Price. A 14-day trial with no card, then a Free plan or Pro.

What it can't do. It's a mail app, not a plug-in, so you read your Outlook mail in Alrighty instead of in Outlook. It doesn't change Outlook's own Junk settings, and it doesn't screen mail on your phone first. It has no calendar and opens only your own mailbox, not shared ones. A work account may need your IT admin's approval, as our Outlook accounts guide explains. It takes iCloud, Gmail and Outlook accounts only, and it's new, with no long track record.

Pick it if you read an Outlook.com or Microsoft 365 account on a computer and want the scams and cold mail that Outlook missed caught and kept out.

Outlook's built-in junk filter: best free filter for every Outlook account

Every Microsoft account gets a junk filter on Microsoft's servers, on by default, in every app. Microsoft says "Mail identified as possible junk email can be automatically moved to the Junk Email folder," and malware in it is disabled (Microsoft). For companies, "These protections are included in all organizations with cloud mailboxes," and they're on by default for anti-malware, anti-spam and anti-phishing (Microsoft Learn).

How you train it. Mark what it missed as junk, and mark what it got wrong as not junk. In Outlook.com, use Report > Report phishing for a fake sender (Microsoft).

What it can't do. Junk is kept only for a while: "Junk email is retained for 30 days before it is automatically deleted and is not recoverable." It doesn't list the cold senders it let in. A report doesn't block: Microsoft says a sender you report as phishing "is reported but is not blocked from sending you additional messages."

Pick it if you have any Outlook account. It's already on, so the question is only what to add.

Junk filter levels: best for classic Outlook on Windows

The protection levels most guides talk about live in classic Outlook for Windows. Select Home, then in the Delete group select Block, then Junk E-mail Options (Microsoft). "By default, the Junk Email Filter protection level is set to No Automatic Filtering."

• No Automatic Filtering. The filter is off, but "messages are still evaluated by using the domain names and email addresses in your Blocked Senders List."
• Low. For when you "want to filter only the messages that are the most obvious junk."
• High. For when "you receive lots of junk messages." Microsoft recommends you "occasionally check the Junk E-mail folder."
• Safe Lists Only. "This is the most restrictive option." Anything not from your Safe Senders or to your Safe Recipients is junk.

You can also have it delete suspected junk instead of moving it, which "takes away your ability to review messages for possible false positives."

What it can't do. These levels work only in classic Outlook for Windows. Microsoft's page applies to Outlook for Microsoft 365, Outlook 2024 and Outlook 2021. They don't exist in the new Outlook, on the web, or on a Mac.

Pick it if you still use classic Outlook on a Windows PC. Try High and check Junk for a week.

Safe senders and Blocked senders: best for fixing the filter's mistakes

Safe senders and Blocked senders are the controls every Outlook account has, and they're kept on the server, so they work in every app. Open Settings, Mail, Junk email in Outlook on the web or the new Outlook for Windows (Microsoft).

• Blocked senders and domains. Select Add blocked sender. "If you want to block all email from a domain, enter the domain name." Blocked mail goes to Junk.
• Safe senders and domains. Select Add safe sender. "Messages from addresses or domains on the safe senders list won't get moved to your Junk Email folder."
• Safe senders only. The junk settings' Filters section has Only trust email from addresses in my Safe senders and domains list and Safe mailing lists (Microsoft Learn). Everything else goes to Junk.

For work accounts. Your company's filter runs first. Microsoft warns that "The server that hosts your mailbox may have junk email filtering settings that block messages before they reach your mailbox" (Microsoft).

What it can't do. A block works on one address or domain, and scams and cold mail change address often. Never block a shared domain such as gmail.com or outlook.com. The steps for other apps are in how to block a sender in Gmail, Outlook and Apple Mail.

Pick it if the filter keeps moving one real sender to Junk, or one domain keeps getting through.

Microsoft 365 advanced security: best for Outlook.com at home

A Microsoft 365 Personal or Family subscription adds checks to Outlook.com. "Outlook.com scans the attachments for viruses and malware using advanced detection techniques that provide a higher level of protection than the free version," and removes a dangerous file. It also checks "whether the links are related to phishing scams," and sends you to a warning page if you click a suspicious one (Microsoft).

Where it works. In the cloud, "so you will be protected no matter how you access your email," including in Alrighty, Apple Mail or Outlook for Mac. It turns on by itself for addresses ending in @outlook.com, @hotmail.com, @live.com and @msn.com. A Family plan shares it "with up to 5 others."

What it can't do. It doesn't cover a Gmail or Yahoo account added to Outlook. It checks links and files, so it doesn't catch cold mail or a scam with no link.

Pick it if you already pay for Microsoft 365 Personal or Family. Check that it's on.

Microsoft Defender for Office 365: best for a company on Microsoft 365

Defender for Office 365 is Microsoft's paid layer on top of the built-in filter for work and school mailboxes. Microsoft calls it a ladder: built-in protection for every cloud mailbox, then Plan 1, then Plan 2 (Microsoft Learn).

What it adds. Plan 1 adds "User and domain impersonation protection," "Mailbox intelligence impersonation protection," Safe Attachments and Safe Links in email. That targets the fake-CEO and lookalike-domain mail that spam filters let through.

Price. Plan 1 is "Included in some Microsoft 365 subscriptions that cater to small to medium-sized businesses (for example, Microsoft 365 E3/G3 and Microsoft 365 Business Premium)." It's also "available as an add-on subscription to many Microsoft 365 subscriptions." Microsoft's pages we read didn't show a price. There's a 90-day trial of Plan 2.

What it can't do. You can't buy it for a personal Outlook.com account. An admin turns it on and sets the policies for the whole company.

Pick it if you run IT for a company on Microsoft 365, or you can ask the person who does.

SpamSieve: best for keeping Outlook for Mac

SpamSieve is a Mac spam filter that works inside the mail app you already use, including Outlook. It "learns and adapts to your mail" and "does not transmit your mail data anywhere" (C-Command). It supports macOS 10.13 High Sierra through macOS 27. It costs $39.99, or $63.98 for a family or 2 users (store), with a free trial.

With Outlook. You select Enable spam filtering for Inbox in SpamSieve's settings, then train it with Train as Spam and Train as Good. "SpamSieve will process new mail automatically every minute, moving spam messages from Inbox to Junk Email" (manual).

The catch. It needs legacy Outlook. "SpamSieve uses AppleScript to communicate with Outlook, which is currently only supported in the legacy mode." Some versions of Outlook have no switch back, and the old and new Outlook keep separate mail storage. C-Command says "Microsoft expects to remove Legacy Outlook in October 2029" (manual).

What it can't do. It filters only while your Mac is on and Outlook is open. It doesn't unsubscribe you or list cold senders.

Pick it if you keep legacy Outlook for Mac and want a stronger filter that never sends your mail anywhere.

Clean Email Screener: best for holding back strangers in Outlook.com

Clean Email connects to your mailbox and works "by connecting to your mailbox directly and analyzing and cleaning emails in the cloud," so it works with any Outlook app (Clean Email). Its Screener "intercepts messages from new senders and safely holds them in quarantine for your review," and you allow or block each sender (Screener).

What it says about Outlook. Clean Email's own Outlook guide calls the Screener "a second checkpoint" next to Outlook's filter, not a replacement (Clean Email).

What it can't do. You must approve every new sender. One more company reads your mailbox on its servers. Its plans page showed no prices when we read it.

Pick it if strangers are the problem and you'd rather approve each one than trust a filter.

SpamTitan: best for a business that wants a second filter in front of Microsoft 365

SpamTitan is a business email filter that "blocks phishing, malware, spam, viruses, and other advanced threats pre-delivery." It says it "Works seamlessly with M365, allowing you to supplement its native email security," with allow lists, block lists and greylisting, and it sends users quarantine reports (SpamTitan). It was the first result for this search when we checked.

Price. By quote. Its pricing page asks for a business email and whether you are an MSP, an internal IT team or a reseller. There's a free trial.

What it can't do. It's for organizations that control their own mail domain, set up by IT. It isn't something you add to a personal Outlook.com account or to the Outlook app.

Pick it if you run mail for a company and want a filter from another vendor before Microsoft's.

MailWasher: not for a Mac

MailWasher lets you preview mail on the server and delete spam before it downloads, and it lists Outlook among the services it works with. Its download page answers "Is there a Mac version? Not currently. MailWasher Pro is Windows-only" (MailWasher). On a Mac, use one of the options above.

How to choose

• An Outlook.com or Microsoft 365 account on a Mac or PC, with scams and cold mail caught and kept out: Alrighty.
• Any Outlook account, free: Outlook's own filter. Mark what it gets wrong.
• Classic Outlook on Windows: raise Junk E-mail Options to High.
• One sender or domain the filter keeps getting wrong: Safe senders or Blocked senders.
• Outlook.com, and you pay for Microsoft 365 Personal or Family: advanced security is already on.
• A company on Microsoft 365: Defender for Office 365, through your admin.
• Legacy Outlook for Mac, with a filter on your Mac: SpamSieve.
• Strangers held for you to approve: Clean Email's Screener.
• A second business filter before Microsoft's: SpamTitan.

Questions

Where is the spam filter in the new Outlook?

In the new Outlook for Windows and Outlook on the web, open Settings, Mail, Junk email. You'll find Blocked senders and domains, Safe senders and domains, and a filter that trusts only your safe senders. The protection levels from classic Outlook's Junk E-mail Options aren't there.

Does Outlook for Mac have a junk filter?

Outlook for Mac relies on the filter on Microsoft's servers, which runs for Outlook.com and Microsoft 365 accounts before mail reaches the app. Microsoft's help we found describes no protection level setting for the new Outlook for Mac. SpamSieve adds a filter on the Mac, in legacy Outlook only.

Why is Outlook sending real email to Junk?

The filter guessed wrong, or the sender's domain failed a check. Mark the message as not junk, and add the sender to Safe senders. In classic Outlook, a level of High or Safe Lists Only catches more real mail, so try Low.

Does marking email as junk in Outlook block the sender?

No. It moves the message and helps train the filter. Microsoft says a sender you report as phishing "is reported but is not blocked from sending you additional messages." Add the address or domain to Blocked senders as well.

Can I use a third-party spam filter with Outlook.com?

Yes, if it connects to your mailbox rather than to your company's mail domain. Clean Email and Norton Safe Email work this way. A mail app such as Alrighty adds its own checks on your computer. Business gateways such as SpamTitan need a domain your company controls.