Yammer now has the added functionality of external groups, to go along with external networks and external messaging. When should you use each option, and what are the implications? We will see below that a major differentiator is the scope of the access given to the person who is external to your organization. It should be noted that in all the cases presented here, the external person being invited must be a member of a Yammer network in their own organization. You cannot add a consumer address, such as @outlook.com, as an external participant. External Messaging Within your internal Yammer network, members can add contacts with external email addresses to a conversation by adding them to the cc: notification field in a post. This is referred to as external messaging. When this is done, the person with the external email address will see the conversation in their Yammer Inbox. As shown below, they will be able to see the post, its replies and any attached files, but nothing else in the group: However, the external party should be aware that anything they post in a conversation they are invited to, will potentially be visible by anyone in your organization, not just the members of the group where the conversation takes place. External Groups In Yammer, external groups actually live on your Yammer network like your regular groups. The difference is that you can invite a person to be a member of the group when they have an email address from outside of your organization. If the invitation is accepted, then they can see all posts, files and notes within that group. Only the group administrators can invite an external party to access the group, and the external party must already be a member of a Yammer network in their own organization. This means that, by default, anyone in your organization can invite an external party by being the creator, and hence administrator, of a new external group. External Network If you create an External Network in Yammer, then you are creating a new Yammer Network that is separate from your main internal Yammer network. The two networks are distinct – you can invite external contacts to be members of the external network. Members of the external network cannot see the contents of your internal Yammer network. Admin Control Yammer Network administrators can control whether or not members can create external networks and external groups, or use external messaging. However, by default, anyone in your Yammer network can create both public and private external groups. Currently, disabling members’ ability to create external groups and use external messaging requires a call to Microsoft support – you will not find those options on the Yammer administration pages.