I am sorry but Yammer has been the single most atrocious thing that has been unleashed in organisations.

It is normally touted as some form of magic where everyone needs to get involved and keep everyone up to date. It is simply a waste of productive time as it tries to recreate a twitter/facebook style social media mess of which its value is over inflated.

Use Slack or a wiki or any other sort of collaboration tool that allows for better communication without the hyped hipster propaganda of corporate twitter. I have never worked in an organisation where Yammer added any real value to those who had to deliver. It seemed a great way though for those with too much time and too little output to look busy and impress their often clueless managers come annual review time.