Outlook is marking ALL my emails as junk

Use the built-in Junk Email settings and lists to stop legitimate messages being treated as junk, and check for any external causes such as a mobile device.

1. Check Junk Email protection level in Outlook for Windows
   1. In Outlook, select Home.
   2. In the Delete group, select Block > Junk E-mail Options.
   3. On the Options tab, review the protection level:
      • If it is set to High or Safe Lists Only, change it to Low or No Automatic Filtering.
      • If Safe Lists Only is selected, any sender not on the Safe Senders or Safe Recipients lists will be treated as junk, which matches the behavior described.
   4. Select OK to apply the change.
2. Review Safe Senders, Blocked Senders, and Safe Recipients
   1. In the same Junk E-mail Options dialog, check the Blocked Senders tab.
      • Remove any domains or addresses that should not be blocked.
   2. On the Safe Senders tab, confirm important senders and domains are listed.
   3. On the Safe Recipients tab, verify that any groups or addresses that should always be allowed are present.
   4. On the Junk Email options page (if using Outlook on the web or light version), ensure the option Treat all email as junk unless it comes from someone in my Safe Senders or Safe Recipients lists, or from senders in my organization is not selected, as this forces almost everything into Junk.
3. Turn off overly aggressive behavior (if enabled)
   1. In Junk E-mail Options, on the Options tab, make sure Permanently delete suspected junk email instead of moving it to the Junk E-mail folder is not selected unless this behavior is desired. This option is risky because it prevents review of false positives.
4. Check for external causes (for example, Samsung mobile device)
   • If a Samsung mobile device with the default mail app is connected to the same mailbox, its spam addresses feature can cause messages to be moved to a Junk or Unwanted folder even if Outlook is configured correctly.
   • On the Samsung device:
     1. Open the email app.
     2. Press the Menu key > Settings > General Settings.
     3. Select Spam addresses and remove any entries that should not be treated as spam (for example, the corporate domain or commonly used senders).
5. If using Outlook on the web in parallel
   • Sign in to Outlook on the web.
   • Go to Settings > Mail > Junk email or Block or allow.
   • Under Safe senders and recipients, add important senders or domains.
   • Under Blocked senders and domains, remove any legitimate senders or domains.
   • Select Save.

After adjusting the Junk Email protection level, lists, and any mobile-device spam settings, new messages from legitimate senders should start arriving in the Inbox instead of Junk. Periodically review the Junk Email folder for a while to confirm that false positives have stopped.

References:

• New email messages automatically move to the Junk folder in Microsoft Outlook
• Change the level of protection in the Junk Email Filter in Outlook
• Options > Junk Email
• Block or allow (junk email settings)
• Filter junk email and spam in Outlook