How to Stop Unknown CC Addresses and Outlook Spam Rules
Question details
The user needs to remove unknown CC addresses automatically added to outgoing emails and fix nondelivery reports caused by unauthorized inbox rules.
- Product
- Microsoft Outlook
- Device & OS
- not provided
- Scenario
- Sending emails and managing account security after suspicious mailbox behavior.
- Observed behavior
- Unknown addresses are automatically added to the CC field, and nondelivery reports show a full mailbox alongside an Inbox Rules Agent header, indicating a potential account compromise.
Before modifying your settings, it is highly recommended to disconnect your device from the internet to prevent further unauthorized access, and prepare to update your account passwords.
Inspect and Remove Suspicious Inbox and Forwarding Rules
Check your Outlook web settings to manually delete any unauthorized rules that automatically forward or CC your emails to unknown addresses.
Hackers often create hidden inbox rules to quietly forward or CC your emails to their own accounts. Removing these rules is the most critical step to stopping the behavior.
Open your browser and navigate to https://outlook.office365.com/mail/ to access the web version of Outlook, which bypasses any local client corruption.
Click on the Settings (gear) icon located in the top right corner of the screen, then select 'View all Outlook settings' at the bottom of the pane.
Navigate to 'Mail' > 'Rules'. Carefully review the list of rules. If you see any unfamiliar rules, especially those mentioning forwarding or CCing, click the trash can icon next to them to delete them.
Go to 'Mail' > 'Forwarding'. Ensure that 'Enable forwarding' is turned off. If it is enabled with an unknown email address, uncheck the box and save your changes.
Run a Full Antivirus Scan and Secure Your Account
Eliminate potential malware on your computer and update your credentials to lock out unauthorized users.
Create a New Outlook Profile and Clear Temporary Files
If the issue persists in the desktop app after clearing web rules, creating a fresh Outlook profile will bypass local corruption and hidden agent cache.
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Frequently Asked Questions
Why are unknown addresses suddenly appearing in my CC field?
This typically occurs if your email account has been compromised. A malicious user may have logged in and set up hidden inbox rules to automatically CC or forward your outgoing emails to their address to monitor your communications.
Will changing my password automatically stop the unauthorized CC rules?
No. Changing your password stops the hacker from logging back into your account, but it does not remove the forwarding or CC rules they already created. You must manually delete these suspicious rules in your Outlook settings.
How can I tell if my Outlook account has been hacked?
Common signs of a compromised account include unexpected nondelivery reports (bounce-backs), emails in your Sent folder that you did not write, unfamiliar inbox rules, and complaints from contacts receiving spam from your address.
