Fix Outlook Sending Blind Copies of Messages to Administrator
Question details
An administrator unexpectedly receives blind copies of messages sent by an Outlook user, even though the sender has not created any local Outlook rules for this behavior.
- Product
- Microsoft Outlook
- Device & OS
- not provided
- Scenario
- A user is sending normal emails, but a hidden copy is being automatically routed to an administrator's inbox.
- Observed behavior
- Blind copies (BCC) of outbound messages are automatically generated and delivered to an administrator account without any client-side configuration prompting it.
Ensure you have administrator privileges and access to the Exchange Admin Center, as this issue is typically caused by server-side routing configurations rather than local client settings.
Disable the Exchange Mail Flow Rule
Identify and remove the organization-level Exchange mail flow rule that is automatically redirecting copies of the user's emails to the administrator.
When no local Outlook rule exists, this behavior is almost always caused by an Exchange server mail flow rule (transport rule) set up by an administrator to monitor or backup outgoing messages.
Log in to the Microsoft 365 or Exchange admin portal using an account with Exchange Administrator credentials.
On the left navigation pane, click on 'Mail flow' to expand the menu, then select 'Rules'.
Review the list of active transport rules. Look for a rule configured with an action like 'Bcc the message to' or 'Send a copy to' pointing toward the administrator's email address.
Select the offending rule. If it is no longer needed, click the 'Delete' (trash can) icon. Alternatively, uncheck the 'Enable' toggle to turn it off temporarily without deleting it.
Run an Exchange Message Trace
If no obvious mail flow rule is found, utilize a message trace to track exactly how the message was processed and redirected by the server.
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Frequently Asked Questions
Can local Outlook client rules cause an administrator to receive blind copies?
Yes, it is possible for a user to create a local rule in their Outlook client to automatically CC or forward messages. However, if no such local rules exist, the issue is almost certainly caused by a server-side Exchange transport rule.
What is an Exchange mail flow rule?
Also known as a transport rule, a mail flow rule is a server-side setting in Microsoft Exchange that automatically takes action on messages in transit. It can be used to block, append disclaimers, or BCC emails based on specific sender, recipient, or content conditions.
How long does it take for a message trace to generate results?
For messages sent within the past 7 days, a message trace usually returns results within a few minutes. For messages older than 7 days, you must request an extended historical trace, which can take several hours to generate.
