[Deliverability] Trusted sender allowlisting in Microsoft 365 (warnings/spam/quarantine)

1. Add the Trusted Sender to the Allow List via Exchange Online Protection (EOP)

Step 1: Sign in to the Microsoft 365 Admin Center

Go to the Microsoft 365 Admin Center.

Sign in with your admin account.

Step 2: Go to the Exchange Admin Center

Navigate to Admin centers and click on Exchange.

This will open the Exchange Admin Center.

Step 3: Create a Transport Rule

In the Exchange Admin Center, go to Mail flow, then Rules.

Click on + and select Create a new rule.

Give the rule a name, such as “Whitelist Trusted Sender”.

Step 4: Configure the Transport Rule

Under Apply this rule if…, select The sender… > domain is.

Enter the domain of the trusted sender (e.g., trustedsender.com).

Under Do the following…, select Modify the message properties… > set the spam confidence level (SCL) and set it to -1 (which means the message will never be marked as spam).

Click Save to save the rule.

2. Add the Sender to the Allow List via Microsoft Defender for Office 365

Step 1: Go to the Microsoft 365 Defender Admin Center

Go to the Microsoft 365 Defender Admin Center.

Sign in with your admin account.

Step 2: Add the Trusted Sender

Go to Threat policies and click on Anti-spam policy.

Click Create policy or edit an existing policy.

In the anti-spam policy settings, go to Allowed and blocked senders and domains.

Add the email address or domain of the trusted sender to the Allowed senders and domains list.

Save the changes.