How to block email facing our domain form external ?

[Tien Ngo Thanh]

Hello

       please help me define rule or any option to prevent facing our domain email form external send to internal .I see from email address internal but from IP then external not in office365.

Best Regards,

Thanks

[#2]

I'm not sure I understand the question. Are you trying to prevent people from spoofing your domain? If so, you will have to deploy SPF, DKIM and DMARC and/or use the advanced protection ATP offers. A simpler solution is to define a transport rule that acts on external messages that have your domain in them, see the example here: https://support.knowbe4.com/hc/en-us/articles/212679977-Domain-Spoof-Prevention-in-Exchange-2013-201...

[#3]

1. I just try create rule as your guide and continue monitor

2. We also has client APT , how to configure ATP to prevent from spoofing our domain ? 

3. And current i see DKIM only enable on domain yhn.mail.onmicrosoft.com and yhn.onmicrosoft.com but custom my domain then not enbable , Now i must enable it ? what effect outgoing email or imcomming email when enable it ?

[#4]

Hello   

     I create rule as your guide 

    - Sender outside 

   - sender is domain math our domain

   - do the folowing is send report to monitor this rule

    But i met a problem is when gmail (not spoofing mydomain) send email inside and if inside has set rule forward outside then it will match this rule .in here seem it see email forward as Resent-From should rule match, how to fix it ?

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