How do I turn off Outlook Classic spam filtering? It's useless.

Question

I am currently spending an extra 15 minutes per day going through my spam folder to restore ALL of the filtered mail, marking them all as "Unread", keeping the legitimate ones (because Outlook gets it wrong a LOT), and then using my 3rd party app to properly filter, the way I would like to have it done. I have 2 separate computers, accessing several email accounts, none of which are Microsoft based. This filtering only started last week. I am using Outlook Classic with Office 365. How do I stop Outlook from filtering spam at all?

Answer 1

Hi Claire & Leigh Jensen,

Welcome to Microsoft Q&A forum. 

If the registry change was applied correctly, that means policy setting disables client-side junk filtering in classic Outlook. After that, junk handling is done on the service side, not by Outlook’s local junk filter. The important clue in your update is that “SPAM” is being added to the subject line. If that is happening after Outlook’s client-side junk filter has been disabled, then the tagging is likely being applied before the message reaches Outlook by the mail service, a security filter, or another filtering layer. In that situation, Outlook itself would only be displaying the message as delivered.

You can kindly check these:

• Check Outlook rules to make sure there isn’t a rule moving or processing messages based on the subject.
• Check the internet headers of one tagged message. In classic Outlook, you can open the message and go to File > Properties to view the headers.

If the headers point to a provider or filtering service, the next step would be to adjust settings (or contact support) for the email hosting provider / spam filter / security gateway / third‑party filtering product involved, since Outlook client settings cannot override upstream tagging.

Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas only.

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Answer 2

@Claire & Leigh Jensen said

This filtering only started last week

If you didn't make any changes to your Outlook config, I can not explain.

then using my 3rd party app to properly filter

Perhaps the change was in your external filter program?

Outlook Classic - How do I stop Outlook from filtering spam at all?

The registry change suggested by the Q&A Assist answer is bogus. The correct setting is:

• HKEY_CURRENT_USER\Software\Policies\Microsoft\office\16.0\outlook
• DWORD: DisableAntiSpam
• Value of 1 disables the junk filter, 0 enables it

See: https://www.slipstick.com/outlook/how-to-disable-outlooks-junk-email-filter/

If you do it right, the Junk button in the Delete group will be disabled.

Answer 3

To stop spam filtering in classic Outlook and let the third‑party filter do the work, there are two layers to address:

1. Turn Outlook’s Junk Email Filter to the lowest level
2. Completely disable client‑side junk filtering via registry

1. Set Junk Email Filter to “No Automatic Filtering”

Do this in classic Outlook on each computer/profile:

1. In Outlook, select Home.
2. In the Delete group, select Block > Junk E-mail Options.
3. On the Options tab, choose No Automatic Filtering.
   • Note: Even with this setting, messages are still evaluated against your Blocked Senders List. To fully stop Outlook from acting on those, remove entries from the Blocked Senders list.

This minimizes Outlook’s own filtering but does not fully disable it.

2. Disable Outlook client junk filtering via registry (classic Outlook)

To stop classic Outlook from doing any junk filtering at all and rely only on server/third‑party filtering, set the policy key on each Windows profile that uses Outlook:

1. Close Outlook.
2. Open Registry Editor (regedit.exe).
3. Navigate to: HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\office\16.0\outlook\options\mail
   • Create the keys/path if they don’t exist.
4. Create a new DWORD (32-bit) Value named: JunkMailClientScanDisabled
5. Set its value to 1.
6. Close Registry Editor and restart Outlook (or reboot Windows).

After this change, all junk filtering is done on the service/third‑party side; Outlook’s client junk filter is disabled.

If spam is being filtered by Microsoft 365 (service‑side)

If any of the accounts are hosted in Microsoft 365 and a non‑Microsoft spam filter is already in front, configure Exchange Online to bypass spam filtering using a mail flow rule that sets the spam confidence level (SCL) appropriately, as described in Use mail flow rules to set the spam confidence level (SCL) in messages. Malware and high‑confidence phishing scanning cannot be skipped.

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References:

• Change the level of protection in the Junk Email Filter in Outlook
• Outlook Junk filtering is running but the Junk Email Options settings are removed
• Frequently asked questions - Anti-spam protection
• Overview of the Junk Email Filter in classic Outlook
• 10 tips on how to help reduce spam