Send & Receive Issues

How to Redirect Office 365 Emails and Change the Subject

Steve K Oct 9, 2026 869 views

Question details

The user wants to automatically redirect emails to another address while appending or modifying text in the subject line to easily identify them.

How to Redirect Office 365 Emails and Change the Subject

Product: Microsoft 365 Exchange Online
Device & OS: not provided
Scenario: Redirecting emails between different Microsoft 365 tenants while attempting to keep the redirected messages easily identifiable.
Observed behavior: Microsoft 365 does not support automatic subject changes when the source and destination accounts reside in different tenants.

Before you start

Log into the destination email account via Outlook on the web, as you will need to configure local inbox rules to categorize the redirected messages.

Solution 1Recommended

Use Outlook on the Web Rules to Categorize Redirected Messages

Since cross-tenant subject modification is restricted, use an inbox rule on the receiving account to automatically mark and color-code incoming redirected emails.

When dealing with accounts in different Microsoft 365 tenants, Exchange Online prevents modifying the subject line during an automatic redirection for security and compliance reasons.

Instead of changing the subject, you can achieve a similar result by setting up a rule in the destination mailbox that automatically assigns a specific category to emails received from your source address.

Open Outlook Settings

Sign in to Outlook on the web for your destination account. Click the gear icon (Settings) in the upper-right corner of the screen.

Navigate to Rules

In the Settings menu, go to 'Mail' in the left pane, and then select 'Rules'.

Add a New Rule

Click on 'Add new rule'. Give your rule a descriptive name, such as 'Redirected Emails'.

Set the Condition

Under 'Add a condition', choose 'To' or 'Recipient address includes' and enter the email address of the source account that is redirecting the emails.

Set the Categorize Action

Under 'Add an action', select 'Categorize' and choose an existing color category or create a new one to distinctly highlight these messages in your inbox.

Save the Rule

Click 'Save' at the bottom. Future redirected emails will now be automatically categorized and highlighted.

Use Outlook on the Web Rules to Categorize Redirected Messages

Alternative Method: If you require subject line modification and are within the same tenant, an Exchange administrator can achieve this using Mail Flow rules in the Exchange Admin Center.

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Frequently Asked Questions

Why can't I change the email subject when redirecting between Office 365 tenants?

Microsoft 365 restricts automatic subject changes and certain mail flow modifications across different tenants to prevent spam relaying, phishing, and to maintain strict security compliance between external organizations.

What is the difference between forwarding and redirecting an email in Outlook?

Forwarding an email adds 'FW:' to the subject line and shows your account as the sender. Redirecting sends the message exactly as it was received, preserving the original sender's email address in the 'From' field.

Can I color-code redirected emails in the Outlook desktop app?

Yes. While the web version is recommended for initial setup, you can also open the Outlook desktop app, navigate to File > Manage Rules & Alerts, and create a rule to assign a color category to messages forwarded or redirected from a specific address.

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