Information Rights Management (IRM), available in Microsoft Outlook 2013 and Outlook 2016, allows people to specify access permissions to email messages. Your organization must install and deploy IRM before you can use it. For more information about IRM in Outlook, see Introduction to IRM for email messages.
Important: You can view IRM-protected mail using Outlook RT, but you can't send. Want to see what version of Office you're using?
Messages you receive with restricted permission are identified by an icon that appears in the message list of your Inbox. The contents of a rights-managed message don't appear in the Reading Pane.
To open the message:
In the message list, double-click the message to open it.
Note: As the recipient, you can't print, forward, or copy the rights-managed message. However, you can reply to the sender. Your reply has the same restrictions to the recipient (original sender) as the original message.
The first time that you open a message that uses restricted permission, Outlook must connect to a licensing server to verify your credentials and download a use license. The use license defines the level of access that you have to a file. After the certificate is installed, you can view the contents of the message by opening the message.
More about how to download credentials
If your organization uses an IRM server, your administrator can advise you on how to set permissions. However, many home and personal email accounts don't use an IRM server. In that case, your first attempt to set permissions on a message opens a dialog box in which Outlook prompts you to sign up for a free trial on an IRM server. A temporary credential is available by clicking Yes and signing up for a Rights Management (RM) account certificate for your outgoing email address. Your email address must be Microsoft account enabled. If you don't have a Microsoft account email address, you can quickly get a free Microsoft account.