External Yammer group to allow outside org collaboration
We discussed before about Yammer as Enterprise social network tool that can be standalone or part of Office 365, for more about Yammer check this link of previous blogs
In Yammer if you would like to connect not only with company/org employees but with external contacts, you can make that using external groups, follow those steps to activate it:
Go to admin center and then select Yammer admin, or go inside your yammer.com and select Network you would like and then pres on settings
then press on security you will find section in the middle to allow external messaging.
Then select groups
Then create new group
Choose external network
You will get this network where you can start adding external contacts.