First create universal group and add users to the group the mail enable it

With the following command from the exchange PowerShell

Enable-DistributionGroup -Identity “groupName”

After its enabled

Run the following command

send on behalf off

(run the command from the exchange powershell)

Set-MailPublicFolder “\publicfoldername” -GrantSendOnBehalfTo “Groupname”

send as

For the send as go to properties of the distribution group from the ECP schange link then go to delivery options

Add the group

Use your Office 365 credentials to sign in to Yammer

Then choose SharePoint

one

This is the situation now before enabling the yammer.com feature there is now office 365 log in

SharePoint admin center

And check the Use Yammer.comService radio button

Now you can go to yammer website

https://www.yammer.com/companyname.com/#/home

change the company name with your domain name

And then go to network Admin

Now the option is there

Check the enforce office 365 identity in yammer

Make sure to notify users cause all users will be logged out and they will have to re login again using the office 365 account

After you accept you will have a new option for blocking users how don’t have yammer license

Microsoft System Admins