Forum Discussion

Iron Contributor

Feb 25, 2019

How to block email facing our domain form external ?

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....

Exchange Server

office 365

VasilMichev

MVP

Feb 25, 2019

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-2013-2016-Office-365

Tien Ngo Thanh

Iron Contributor

Feb 26, 2019

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 ?