Yammer ETR to control external messaging




I have followed the guidance to enforce Exchange Online Exchange Transport Rules (ETRs) in Yammer. I have created a rule in Exchange Online to apply if the recipient is located 'Outside the organization' and the sender address includes '@yammer.com' then 'deliver the message to hosted quarantine'. I gave it sufficient time (couple of hours) before testing. However, I can still send external messages and also invite external members to my Yammer group. Checking the Exchange Online quarantine shows nothing. 


Any ideas why this is not working? The last synced at shows blank in Yammer external messaging settings. Not sure if this is an issue.


Does Yammer use our Exchange Online service for sending external messages and group invites?


Would Yammer honor the rule if modified to setup a white list of external email addresses \ domains by adding Exception ?

13 Replies

Thought I'll leave an update. Opened a case with Microsoft and its being investigated by the Yammer team. Will post if there is a resolution. At the moment it seems like ETR in Yammer doesn't work as it says on the tin, the only other option would be to disable in the back-end. I wonder if anyone else have successfully implemented ETR in Yammer?

Hi Paul, were you able to get this working? What was the resolution? I have the same issue with ETR and Yammer external messaging and I am interested in a solution if you have one. Thanks.

Same issue too. No resolution for the moment.


I found "These settings will take approx. 30 hours to sync and disable creation of External Groups to all users. We cannot authorise for only admins. External group creation will be disabled for all users including admins."




No I was never able to get this to work, it's broken. Microsoft disabled external group creation in the backend. This disabled external groups across the board though.

Have done this multiple times and it always worked correctly. Have it enabled now for one of my customers without issues. No need to go into Exchange Online. There is a setting in the Yammer admin portal under "security" named:


"Enforce your Exchange Online Exchange Transport Rules (ETRs) in Yammer"


After enabling that, external messaging was disabled. You do have to reach out to Microsoft support if you want to allow your users to join external groups of other networks. 

That information is not entirely correct. 

In order to disable external messaging in Yammer you require two pieces:

  1.  Enforce your Exchange Online Exchange Transport Rules (ETRs) in Yammer" as per Pooya's comment 
  2. A rule in Exchange online. The rule should look like this:




Two days after, parameter is still not sync (cf. screenshoot)



The Exchange rule (must have one no matters what) as described in official documentation :



looks like this :



Hi Federic,

As mentioned in my earlier post, I had issues with this and I called Microsoft to find a resolution. 

The resolution was to create the Exchange rule as per the screenshot included in my earlier post. It seems that the official documentation is not complete. 

Hope this helps and works for you as well, let me know .



Thank you Carmen for the precision. I try it now and I'd let you know when it will be updated.




Kind regards,


Working fine with your rule Carmen. 

Thank you so much!


Interesting, because that's not the case for the network I'm looking at right now. We only checked that box and users can't create external groups or add external users to conversations. No need to dive into Exchange and this was also not required for other networks where I updated this setting. Not sure why it's not working for you, but for me it's working exactly the way it has been documented by Microsoft. 


Update: just checked the documentation. The Exchange Online part is new. Not sure why they changed it. 

You're right. It needs more tests to validate that the Carmen's rule is responsible of the blocking process. Perhaps it was a coincidence and I should had wait one hour more.
I will test it with 3 tenants : one with the documentation rule, one without rules and one with the carmen's rule.

To be continued....

For tenants in Europe, external groups aren't available!