Block Emails from External Email Addresses or Domains

This guide demonstrates how to Block Emails from External Email Addresses or Domains

1) Validate you have the correct permissions to action this:

You will need either the 'Exchange Administrator' or 'Exchange Recipient Administrator' PIM.

2) Visit this URL: Exchange admin center (microsoft.com)

3) From the left-hand pane, if the link does not take you there... Click the 'Mailflow' drop down and then 'Rules' then look for the 'Rule' named 'Block External', this is highlighted in the image below.

4) Click the 'Block External' and then a pane will appear on the right side, select 'Edit Rule Conditions'

5) Click on the pencil icon highlighted below:

6) Type the domain or email address in the 'Specify Words or Phrases' field then click add. Remember to then click Save!