Block email address exchange admin center

In the Microsoft 365 Admin Center, you can block an email address to prevent it from sending emails to your organization. Here's how:

Method 1: Block an email address using the "Junk email" settings

  1. Sign in to the Microsoft 365 Admin Center with your admin credentials.
  2. Go to Settings > Junk email.
  3. Click on Blocked senders.
  4. Click on Add a blocked sender.
  5. Enter the email address you want to block in the format [email protected].
  6. Click Add.

Method 2: Block an email address using the "Mail flow" settings

  1. Sign in to the Microsoft 365 Admin Center with your admin credentials.
  2. Go to Settings > Mail flow.
  3. Click on Rules.
  4. Click on New rule.
  5. Select Block as the rule type.
  6. Enter the email address you want to block in the format [email protected].
  7. Click Save.

Method 3: Block an email address using PowerShell

  1. Open PowerShell as an administrator.
  2. Run the following command: New-TransportRule -Name "Block <email address>" -Subject "Block <email address>" -Condition @("From", "<email address>") -Action "Reject"
  3. Replace <email address> with the email address you want to block.

Note: When you block an email address, it will not be able to send emails to your organization. However, if the email address is already in your organization's address book, it will not be blocked.

Also, keep in mind that blocking an email address is a global setting that applies to all mailboxes in your organization. If you want to block an email address for a specific mailbox only, you can use the "Mail flow" settings and select the mailbox you want to apply the rule to.