This update is being rolled out over the week.
Yammer is being updated to allow end-users to create Yammer groups with external users. This feature called External Groups does not impact existing groups; if you want to have external user added, you must create a new external group
Create an External Group
- Logon to Yammer
- Click on Create a new group
- Select External Group
- And complete the creation by naming the group and inviting peoples, including external users
NOTE if you administrator has blocked external groups creation, you will not see this option
Block External Groups
If you want to block such external group, you have the following options:
- Block end-users to create external groups: This is the same control you use to block external messaging participants. Blocking users in this fashion ensures that content within your Yammer network will not be made visible to external users via external groups. This means that people in your network will not be able to create external groups
- Allow inbound external groups only: This blocks external group creation BUT still allow end-users to be invited to other external groups (from external networks)
For these options, you need to contact the support
One last option (and which does not require support call) is to use Exchange Transport Rules (ETR).
To do so, you need to logon as a Yammer network admin and access the Security Settings and enforce the use of Exchange Transport Rule