Blocking SMTP from personal MS accounts in Outlook
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Blocking SMTP from personal MS accounts in Outlook


Article ID: 277952


Updated On:


Data Loss Prevention Endpoint Prevent Data Loss Prevention


You want to block all SMTP from endpoint devices unless the sender's email is trusted.
For example, a user adds a personal MS account mailbox to the Outlook client on their corporate laptop and then sends classified information to an external email recipient. 
This should be blocked.
However, the user should still be able to send emails from his/her corporate account.


  1. Create a policy to block the "Protocol is Email/SMTP".
  2. Add a rule for "Protocol > Protocol or Endpoint Monitoring > select Email/SMTP".
  3. Add a Block response rule.
  4. On the Groups tab, add an exception for "Sender/User Matches Pattern".
  5. Either select an already configured "Reusable Sender Pattern" or add your "Sender Pattern" with the "<company>.<domain>", etc., partial email addresses.