Blocking or Allowing Emails in Exchange Online Protection


With the Exchange Online service, you have access to the Exchange Online Protection service for anti-spam and anti-malware functions.

At times, you may find a legitimate email has been marked as Junk (a false positive) and want to allow this through for future emails. Alternatively, you may have received an email that should be blocked or handled as spam (a false negative).

The Exchange Online Protection service allows you to block emails based on the address they come from and the IP address of the sending server.

It is not recommended to configure Allow policies for free-mail domains such as outlook.com or yahoo.com.

Block or Allow by Email Address

  1. Log into the Microsoft 365 Admin Center using global admin credentials for the tenant: https://admin.microsoft.com
  2. Under Admin Centers, select Exchange

Note: If you don’t see the Admin Centers section, press Show More

  1. Go to ‘Protection > Spam Filter

  1. Double click on the Default spam configuration

  1. Select either Allow lists or Block lists

  1. Under Sender block/allow list, select the + icon

  1. Enter the address to block with one-per line

Note: You can also add multiple entries per line separated by a semicolon.

  1. Select OK

  2. Select Save


Block or Allow by Domain

  1. Log into the Microsoft 365 Admin Center using global admin credentials for the tenant: https://admin.microsoft.com
  2. Under Admin Centers, select Exchange

Note: If you don’t see the Admin Centers section, press Show More

  1. Go to ‘Protection > Spam Filter

  1. Double click on the Default spam configuration

  1. Select either Allow lists or Block lists

  1. Under Domain block/allow list, select the + icon

  1. Enter the domain to block with one-per line

Note: You can also add multiple entries per line separated by a semicolon.

  1. Select OK

  2. Select Save

Block or Allow by IP Address

  1. Log into the Microsoft 365 Admin Center using global admin credentials for the tenant: https://admin.microsoft.com
  2. Under Admin Centers, select Exchange

Note: If you don’t see the Admin Centers section, press Show More

  1. Go to ‘Protection > Connection Filter’

  1. Double click on the Default Connection Filter

  1. Select Connection Filtering

  1. Under IP block/allow list, select the + icon

  1. Enter the IP address you want to block

Note: You can block ranges of IPs by entering them in CIDR format (Only /24 & /32 are supported)

  1. Press OK

  2. Press Save